GDScript: Allow "match" to be used as an identifier

This is needed to call the String.match() function.

modules/gdscript/gdscript_tokenizer.cpp

@@ -156,6 +156,18 @@ const char *GDScriptTokenizer::Token::get_name() const {
 	return token_names[type];
 }
 
+bool GDScriptTokenizer::Token::is_identifier() const {
+	// Note: Most keywords should not be recognized as identifiers.
+	// These are only exceptions for stuff that already is on the engine's API.
+	switch (type) {
+		case IDENTIFIER:
+		case MATCH: // Used in String.match().
+			return true;
+		default:
+			return false;
+	}
+}
+
 String GDScriptTokenizer::get_token_name(Token::Type p_token_type) {
 	ERR_FAIL_INDEX_V_MSG(p_token_type, Token::TK_MAX, "<error>", "Using token type out of the enum.");
 	return token_names[p_token_type];

modules/gdscript/gdscript_tokenizer.h

@@ -168,9 +168,8 @@ public:
 		String source;
 
 		const char *get_name() const;
-		// TODO: Allow some keywords as identifiers?
-		bool is_identifier() const { return type == IDENTIFIER; }
-		StringName get_identifier() const { return literal; }
+		bool is_identifier() const;
+		StringName get_identifier() const { return source; }
 
 		Token(Type p_type) {
 			type = p_type;