Add "button_selected" signal to ButtonGroup

scene/gui/button_group.cpp

@@ -60,6 +60,9 @@ void ButtonGroup::_pressed(Object *p_button) {
 
 		BaseButton *bb=E->get();
 		bb->set_pressed( b==bb );
+		if (b==bb){
+			emit_signal("button_selected", b);
+		}
 	}
 }
 
@@ -153,6 +156,7 @@ void ButtonGroup::_bind_methods() {
 	ObjectTypeDB::bind_method(_MD("_pressed"),&ButtonGroup::_pressed);
 	ObjectTypeDB::bind_method(_MD("set_pressed_button","button:BaseButton"),&ButtonGroup::_pressed);
 
+	ADD_SIGNAL( MethodInfo("button_selected",PropertyInfo(Variant::OBJECT,"button",PROPERTY_HINT_RESOURCE_TYPE,"BaseButton")));
 }
 
 ButtonGroup::ButtonGroup() : BoxContainer(true)