Fixes the following GCC 5 warnings:
```
core/io/zip_io.h:128:26: warning: 'zlib_filefunc_def zipio_create_io_from_file(FileAccess**)' defined but not used [-Wunused-function]
core/script_debugger_remote.cpp:110:17: warning: 'ObjectID safe_get_instance_id(const Variant&)' defined but not used [-Wunused-function]
drivers/unix/socket_helpers.h:103:12: warning: 'int _socket_create(IP::Type&, int, int)' defined but not used [-Wunused-function]
drivers/unix/socket_helpers.h:45:15: warning: 'size_t _set_sockaddr(sockaddr_storage*, const IP_Address&, int, IP::Type)' defined but not used [-Wunused-function]
drivers/unix/socket_helpers.h:76:15: warning: 'size_t _set_listen_sockaddr(sockaddr_storage*, int, IP::Type, IP_Address)' defined but not used [-Wunused-function]
editor/editor_fonts.cpp:40:24: warning: 'Ref<BitmapFont> make_font(int, int, int, int, const int*, const Ref<Texture>&)' defined but not used [-Wunused-function]
editor/editor_themes.cpp:85:26: warning: 'Ref<StyleBoxFlat> change_border_color(Ref<StyleBoxFlat>, Color)' defined but not used [-Wunused-function]
editor/import/editor_import_collada.cpp:493:13: warning: 'void _generate_normals(const PoolVector<int>&, const PoolVector<Vector3>&, PoolVector<Vector3>&)' defined but not used [-Wunused-function]
editor/import/editor_import_collada.cpp:524:13: warning: 'void _generate_tangents_and_binormals(const PoolVector<int>&, const PoolVector<Vector3>&, const PoolVector<Vector3>&, const PoolVector<Vector3>&, PoolVector<float>&)' defined but not used [-Wunused-function]
editor/pvrtc_compress.cpp:118:13: warning: 'void _compress_etc(Image*)' defined but not used [-Wunused-function]
modules/etc/image_etc.cpp:89:13: warning: 'void _decompress_etc1(Image*)' defined but not used [-Wunused-function]
modules/etc/image_etc.cpp:93:13: warning: 'void _decompress_etc2(Image*)' defined but not used [-Wunused-function]
modules/gdscript/editor/gdscript_highlighter.cpp:46:13: warning: 'bool _is_whitespace(CharType)' defined but not used [-Wunused-function]
scene/2d/cpu_particles_2d.cpp:510:14: warning: 'float rand_from_seed_m1_p1(uint32_t&)' defined but not used [-Wunused-function]
scene/3d/cpu_particles.cpp:474:14: warning: 'float rand_from_seed_m1_p1(uint32_t&)' defined but not used [-Wunused-function]
scene/resources/default_theme/default_theme.cpp:123:20: warning: 'Ref<Shader> make_shader(const char*, const char*, const char*)' defined but not used [-Wunused-function]
scene/resources/default_theme/default_theme.cpp:130:24: warning: 'Ref<BitmapFont> make_font(int, int, int, int, const int*, const Ref<Texture>&)' defined but not used [-Wunused-function]
```

Had to split `core/io/zip_io.h` into header and .cpp file without 'static' keyword.

Not fixed yet (static definition in header used in some files but not all):
```
modules/websocket/lws_helper.h:111:13: warning: 'void _lws_make_protocols(void*, int (*)(lws*, lws_callback_reasons, void*, void*, size_t), PoolVector<String>, _LWSRef**)' defined but not used [-Wunused-function]
```

Also fixed a couple other warnings missed in previous commits.

This fixes a bug in refprobe blending, but I have no idea when I fixed it. It just started working all of sudden..

Fix build error: inconsistent use of tabs and spaces in indentation

Fixed casting result in float.xml

Did some hacks to it to avoid it from failing on bad geometry.

The float-string parsing result in the documentation was inaccurate. 1e-3 is written as 0.001 when decimal.

-Added hint to not show some properties when running on low end gfx

[DOCS] ButtonList - extra mouse buttons

Fix warnings about wrong member initialization order [-Wreorder]

Fixed Objects do not showing their drop down in debugger.

Fixed Objects do not showing their drop down in debugger

Fixes the following GCC 5 warnings:
```
core/object.h:193:11: warning: 'MethodInfo::flags' will be initialized after [-Wreorder]
core/object.h:192:15: warning:   'PropertyInfo MethodInfo::return_val' [-Wreorder]
core/object.cpp:278:1: warning:   when initialized here [-Wreorder]
core/script_debugger_remote.h:97:6: warning: 'ScriptDebuggerRemote::max_cps' will be initialized after [-Wreorder]
core/script_debugger_remote.h:91:6: warning:   'int ScriptDebuggerRemote::max_messages_per_frame' [-Wreorder]
core/script_debugger_remote.cpp:1086:1: warning:   when initialized here [-Wreorder]
core/script_debugger_remote.h:98:6: warning: 'ScriptDebuggerRemote::char_count' will be initialized after [-Wreorder]
core/script_debugger_remote.h:92:6: warning:   'int ScriptDebuggerRemote::n_messages_dropped' [-Wreorder]
core/script_debugger_remote.cpp:1086:1: warning:   when initialized here [-Wreorder]
modules/bullet/area_bullet.h:102:7: warning: 'AreaBullet::isScratched' will be initialized after [-Wreorder]
modules/bullet/area_bullet.h:92:39: warning:   'PhysicsServer::AreaSpaceOverrideMode AreaBullet::spOv_mode' [-Wreorder]
modules/bullet/area_bullet.cpp:46:1: warning:   when initialized here [-Wreorder]
modules/bullet/collision_object_bullet.h:127:15: warning: 'CollisionObjectBullet::space' will be initialized after [-Wreorder]
modules/bullet/collision_object_bullet.h:117:7: warning:   'CollisionObjectBullet::Type CollisionObjectBullet::type' [-Wreorder]
modules/bullet/collision_object_bullet.cpp:67:1: warning:   when initialized here [-Wreorder]
modules/bullet/godot_ray_world_algorithm.h:48:7: warning: 'GodotRayWorldAlgorithm::m_ownManifol1d' will be initialized after [-Wreorder]
modules/bullet/godot_ray_world_algorithm.h:46:33: warning:   'const btDiscreteDynamicsWorld* GodotRayWorldAlgorithm::m_world' [-Wreorder]
modules/bullet/godot_ray_world_algorithm.cpp:50:1: warning:   when initialized here [-Wreorder]
modules/bullet/godot_result_callbacks.h:91:18: warning: 'GodotAllConvexResultCallback::m_exclude' will be initialized after [-Wreorder]
modules/bullet/godot_result_callbacks.h:89:6: warning:   'int GodotAllConvexResultCallback::m_resultMax' [-Wreorder]
modules/bullet/godot_result_callbacks.h:93:2: warning:   when initialized here [-Wreorder]
modules/bullet/godot_result_callbacks.h:142:18: warning: 'GodotAllContactResultCallback::m_exclude' will be initialized after [-Wreorder]
modules/bullet/godot_result_callbacks.h:140:6: warning:   'int GodotAllContactResultCallback::m_resultMax' [-Wreorder]
modules/bullet/godot_result_callbacks.h:147:2: warning:   when initialized here [-Wreorder]
modules/bullet/godot_result_callbacks.h:168:18: warning: 'GodotContactPairContactResultCallback::m_exclude' will be initialized after [-Wreorder]
modules/bullet/godot_result_callbacks.h:166:6: warning:   'int GodotContactPairContactResultCallback::m_resultMax' [-Wreorder]
modules/bullet/godot_result_callbacks.h:173:2: warning:   when initialized here [-Wreorder]
modules/bullet/godot_result_callbacks.h:195:18: warning: 'GodotRestInfoContactResultCallback::m_exclude' will be initialized after [-Wreorder]
modules/bullet/godot_result_callbacks.h:191:7: warning:   'bool GodotRestInfoContactResultCallback::m_collided' [-Wreorder]
modules/bullet/godot_result_callbacks.h:199:2: warning:   when initialized here [-Wreorder]
modules/bullet/rigid_body_bullet.h:200:9: warning: 'RigidBodyBullet::gravity_scale' will be initialized after [-Wreorder]
modules/bullet/rigid_body_bullet.h:199:9: warning:   'real_t RigidBodyBullet::mass' [-Wreorder]
modules/bullet/rigid_body_bullet.cpp:258:1: warning:   when initialized here [-Wreorder]
modules/bullet/rigid_body_bullet.h:222:28: warning: 'RigidBodyBullet::force_integration_callback' will be initialized after [-Wreorder]
modules/bullet/rigid_body_bullet.h:219:7: warning:   'bool RigidBodyBullet::isTransformChanged' [-Wreorder]
modules/bullet/rigid_body_bullet.cpp:258:1: warning:   when initialized here [-Wreorder]
modules/bullet/rigid_body_bullet.h:220:7: warning: 'RigidBodyBullet::previousActiveState' will be initialized after [-Wreorder]
modules/bullet/rigid_body_bullet.h:208:6: warning:   'int RigidBodyBullet::maxCollisionsDetection' [-Wreorder]
modules/bullet/rigid_body_bullet.cpp:258:1: warning:   when initialized here [-Wreorder]
modules/bullet/soft_body_bullet.h:69:9: warning: 'SoftBodyBullet::total_mass' will be initialized after [-Wreorder]
modules/bullet/soft_body_bullet.h:68:6: warning:   'int SoftBodyBullet::simulation_precision' [-Wreorder]
modules/bullet/soft_body_bullet.cpp:38:1: warning:   when initialized here [-Wreorder]
modules/bullet/soft_body_bullet.h:76:9: warning: 'SoftBodyBullet::drag_coefficient' will be initialized after [-Wreorder]
modules/bullet/soft_body_bullet.h:61:14: warning:   'btSoftBody* SoftBodyBullet::bt_soft_body' [-Wreorder]
modules/bullet/soft_body_bullet.cpp:38:1: warning:   when initialized here [-Wreorder]
modules/bullet/space_bullet.h:97:22: warning: 'SpaceBullet::solver' will be initialized after [-Wreorder]
modules/bullet/space_bullet.h:95:35: warning:   'btDefaultCollisionConfiguration* SpaceBullet::collisionConfiguration' [-Wreorder]
modules/bullet/space_bullet.cpp:333:1: warning:   when initialized here [-Wreorder]
modules/bullet/space_bullet.h:101:23: warning: 'SpaceBullet::soft_body_world_info' will be initialized after [-Wreorder]
modules/bullet/space_bullet.h:99:23: warning:   'btGhostPairCallback* SpaceBullet::ghostPairCallback' [-Wreorder]
modules/bullet/space_bullet.cpp:333:1: warning:   when initialized here [-Wreorder]
modules/gdnative/nativescript/nativescript.h:79:13: warning: 'NativeScriptDesc::base_native_type' will be initialized after [-Wreorder]
modules/gdnative/nativescript/nativescript.h:73:9: warning:   'String NativeScriptDesc::documentation' [-Wreorder]
modules/gdnative/nativescript/nativescript.h:88:9: warning:   when initialized here [-Wreorder]
modules/gdscript/gdscript.h:296:6: warning: 'GDScriptWarning::line' will be initialized after [-Wreorder]
modules/gdscript/gdscript.h:294:4: warning:   'GDScriptWarning::Code GDScriptWarning::code' [-Wreorder]
modules/gdscript/gdscript.h:303:2: warning:   when initialized here [-Wreorder]
scene/3d/physics_body.h:544:7: warning: 'PhysicalBone::simulate_physics' will be initialized after [-Wreorder]
scene/3d/physics_body.h:543:7: warning:   'bool PhysicalBone::_internal_static_body' [-Wreorder]
scene/3d/physics_body.cpp:2502:1: warning:   when initialized here [-Wreorder]
scene/3d/physics_body.h:546:6: warning: 'PhysicalBone::bone_id' will be initialized after [-Wreorder]
scene/3d/physics_body.h:539:12: warning:   'Skeleton* PhysicalBone::parent_skeleton' [-Wreorder]
scene/3d/physics_body.cpp:2502:1: warning:   when initialized here [-Wreorder]
scene/3d/spring_arm.h:44:11: warning: 'SpringArm::mask' will be initialized after [-Wreorder]
scene/3d/spring_arm.h:43:8: warning:   'float SpringArm::current_spring_length' [-Wreorder]
scene/3d/spring_arm.cpp:37:1: warning:   when initialized here [-Wreorder]
scene/animation/skeleton_ik.h:159:11: warning: 'SkeletonIK::target_node_override' will be initialized after [-Wreorder]
scene/animation/skeleton_ik.h:152:7: warning:   'bool SkeletonIK::use_magnet' [-Wreorder]
scene/animation/skeleton_ik.cpp:418:1: warning:   when initialized here [-Wreorder]
scene/resources/tile_set.h:84:9: warning: 'TileSet::AutotileData::size' will be initialized after [-Wreorder]
scene/resources/tile_set.h:83:7: warning:   'int TileSet::AutotileData::spacing' [-Wreorder]
scene/resources/tile_set.h:92:12: warning:   when initialized here [-Wreorder]
scene/resources/tile_set.h:115:12: warning: 'TileSet::TileData::tile_mode' will be initialized after [-Wreorder]
scene/resources/tile_set.h:114:9: warning:   'Color TileSet::TileData::modulate' [-Wreorder]
scene/resources/tile_set.h:120:12: warning:   when initialized here [-Wreorder]
servers/physics/body_sw.h:84:19: warning: 'BodySW::direct_state_query_list' will be initialized after [-Wreorder]
servers/physics/body_sw.h:57:11: warning:   'uint16_t BodySW::locked_axis' [-Wreorder]
servers/physics/body_sw.cpp:756:1: warning:   when initialized here [-Wreorder]
```

Nothing really relevant for us, but it's not a bad consistency
improvement anyway so worth taking.

Move Penner easing equations to thirdparty/misc

It was Godot-ified and integrated into Tween originally (#628)
without mention that it was thirdparty code, but it's actually
derived from https://github.com/jesusgollonet/ofpennereasing.

It's also very bad quality code and should be replaced by a better,
properly-maintained library of easing equations.

Add small thumbnails to the FileSystem file list

SCons: Build thirdparty code in own env, disable warnings

Also remove unnecessary `Export('env')` in other SCsubs,
Export should only be used when exporting *new* objects.

Renaming SimplexNoise refs to OpenSimplexNoise

Because I think github doesn't show history of renamed files
- The original work is done in commit f12a1b88
by JFonS
- Improved Documentation in commit a386af67
- Last change on the files was in commit 463af5b6
- and Fixed compiler warnings in commit e5bbcb8b

SCons: Build core/ in its own environment, move Zlib and Zstd build in core/

Also move Zlib and Zstd's build instructions to core/SCsub.

Added hover_pressed style to CheckBox and CheckButton

Added warning when min_value of range <= 0 while exp_edit is true.

Added step support when exporting integers.

Fixed step value not being respected for ranges in some cases.

Add code example to ArrayMesh class docs

Fix warnings about unhandled enum value in switch [-Wswitch]

Server platform builds (dummy) mobile_vr module.

[DOCS] InputEventMouseButton: correct description for doubleclick property

Fix some wchar_t truncations in TextEdit

Remove socket_helper.h after NetSocket refactor

Add support for onRequestPermissionsResult()

Credit goes to @vanyasem  https://github.com/vanyasem/Godot-AndroidPermissions
But this is a much needed feature to support Android beyond API 21.
Fixed style errors again.