Added

• [PHP 8.1] Added support for readonly properties (through a new MODIFIER_READONLY).
• [PHP 8.1] Added support for final class constants.

Fixed

• Fixed compatibility with PHP 8.1. & tokens are now canonicalized to the T_AMPERSAND_FOLLOWED_BY_VAR_OR_VARARG and T_AMPERSAND_NOT_FOLLOWED_BY_VAR_OR_VARARG tokens used in PHP 8.1. This happens unconditionally, regardless of whether the emulative lexer is used.