Support php 8.0's named argument RFC

[TysonAndre]

Possible heuristics:

Check if the token after the current token is a : (ColonToken). If so, and the current token can be used as a Name if the kind is right. This involves some edge cases, e.g. foo(default: 123) uses DefaultKeyword as a valid parameter name in php 8.0

https://wiki.php.net/rfc/named_params

The implementation PR mentions it accepts an identifier (e.g. else, __namespace__, myName, etc.)

reserved_non_modifiers:
	  T_INCLUDE | T_INCLUDE_ONCE | T_EVAL | T_REQUIRE | T_REQUIRE_ONCE | T_LOGICAL_OR | T_LOGICAL_XOR | T_LOGICAL_AND
	| T_INSTANCEOF | T_NEW | T_CLONE | T_EXIT | T_IF | T_ELSEIF | T_ELSE | T_ENDIF | T_ECHO | T_DO | T_WHILE | T_ENDWHILE
	| T_FOR | T_ENDFOR | T_FOREACH | T_ENDFOREACH | T_DECLARE | T_ENDDECLARE | T_AS | T_TRY | T_CATCH | T_FINALLY
	| T_THROW | T_USE | T_INSTEADOF | T_GLOBAL | T_VAR | T_UNSET | T_ISSET | T_EMPTY | T_CONTINUE | T_GOTO
	| T_FUNCTION | T_CONST | T_RETURN | T_PRINT | T_YIELD | T_LIST | T_SWITCH | T_ENDSWITCH | T_CASE | T_DEFAULT | T_BREAK
	| T_ARRAY | T_CALLABLE | T_EXTENDS | T_IMPLEMENTS | T_NAMESPACE | T_TRAIT | T_INTERFACE | T_CLASS
	| T_CLASS_C | T_TRAIT_C | T_FUNC_C | T_METHOD_C | T_LINE | T_FILE | T_DIR | T_NS_C | T_FN | T_MATCH
;

semi_reserved:
	  reserved_non_modifiers
	| T_STATIC | T_ABSTRACT | T_FINAL | T_PRIVATE | T_PROTECTED | T_PUBLIC
;

identifier:
		T_STRING { $$ = $1; }
	| 	semi_reserved  {
			zval zv;
			if (zend_lex_tstring(&zv, $1) == FAILURE) { YYABORT; }
			$$ = zend_ast_create_zval(&zv);
		}
;