New GDScript tokenizer and parser

Sometimes to fix something you have to break it first.

This get GDScript mostly working with the new tokenizer and parser but
a lot of things isn't working yet. It compiles and it's usable, and that
should be enough for now.

Don't worry: other huge commits will come after this.

modules/gdscript/gdscript_function.h

@@ -180,12 +180,12 @@ public:
 		OPCODE_CONSTRUCT_DICTIONARY,
 		OPCODE_CALL,
 		OPCODE_CALL_RETURN,
+		OPCODE_CALL_ASYNC,
 		OPCODE_CALL_BUILT_IN,
 		OPCODE_CALL_SELF,
 		OPCODE_CALL_SELF_BASE,
-		OPCODE_YIELD,
-		OPCODE_YIELD_SIGNAL,
-		OPCODE_YIELD_RESUME,
+		OPCODE_AWAIT,
+		OPCODE_AWAIT_RESUME,
 		OPCODE_JUMP,
 		OPCODE_JUMP_IF,
 		OPCODE_JUMP_IF_NOT,