don't use TYPE_ARG_TYPES in c-family/
	* c-common.c (check_main_parameter_types): Reindent.  Don't use
	TYPE_ARG_TYPES directly.
	(handle_nonnull_attribute): Likewise.
	(sync_resolve_params): Likewise.
	* c-format.c (handle_format_arg_attribute): Likewise.  Adjust call
	to check_format_string.
	(handle_format_attribute): Likewise.
	(check_format_string): Take a function type to examine instead of
	a type list.  Use a function_arg_iterator to step through argument
	types.

From-SVN: r173384