patch 9.1.0148: Vim9: can't call internal methods with objects

Problem:  Vim9: can't call internal methods with objects
Solution: Add support for empty(), len() and string() function
          calls for objects (Yegappan Lakshmanan)

closes: #14129

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/errors.h b/src/errors.h
index 65ee4e8..0dbc5a5 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -3579,8 +3579,12 @@
 	INIT(= N_("E1410: Const variable not supported in an interface"));
 EXTERN char e_missing_dot_after_object_str[]
 	INIT(= N_("E1411: Missing dot after object \"%s\""));
+EXTERN char e_builtin_object_method_str_not_supported[]
+	INIT(= N_("E1412: Builtin object method \"%s\" not supported"));
+EXTERN char e_builtin_class_method_not_supported[]
+	INIT(= N_("E1413: Builtin class method not supported"));
 #endif
-// E1412 - E1499 unused (reserved for Vim9 class support)
+// E1415 - E1499 unused (reserved for Vim9 class support)
 EXTERN char e_cannot_mix_positional_and_non_positional_str[]
 	INIT(= N_("E1500: Cannot mix positional and non-positional arguments: %s"));
 EXTERN char e_fmt_arg_nr_unused_str[]