Implement rb_parser_str_escape()

- This function does not depend on VALUE
- Instead, it uses rb_parser_stirng_t*
- This function works when --dump=y option passed
- This implementation is a port of the rb_str_escape() function in string.c

ast.c

@@ -792,7 +792,7 @@ ast_node_all_tokens(rb_execution_context_t *ec, VALUE self)
             INT2FIX(parser_token->loc.end_pos.lineno),
             INT2FIX(parser_token->loc.end_pos.column)
         );
-        token = rb_ary_new_from_args(4, INT2FIX(parser_token->id), ID2SYM(parser_token->type_id), str, loc);
+        token = rb_ary_new_from_args(4, INT2FIX(parser_token->id), ID2SYM(rb_intern(parser_token->type->ptr)), str, loc);
         rb_ary_push(all_tokens, token);
     }
     rb_obj_freeze(all_tokens);