Improve GDScript "unexpected token in class body" parser error

This parser error was misleading.

Fixes:
1. Now points at correct line
2. For identifiers, prints out `Identifier "%s"`

modules/gdscript/gdscript_tokenizer.h

@@ -178,6 +178,7 @@ public:
 		String source;
 
 		const char *get_name() const;
+		String get_debug_name() const;
 		bool can_precede_bin_op() const;
 		bool is_identifier() const;
 		bool is_node_name() const;