The pattern and replacement matching behaviour has been changed purely
due to the nature of switching to a standards-compliant library.

One mistake in the previous behaviour was that named groups didn't have
a number. This has been corrected.

As names are actually just an alias of numbered groups,
RegExMatch::get_name_dict() is now get_names() and is a dict
referring to the group number it represents.

Duplicate names are enabled and the with the first matching instance
used.

Due the lack of a suitable equivalent in PCRE2, RegExMatch::expand() was
removed.