io.c (check_format): As a GNU extension...

	* io.c (check_format): As a GNU extension, allow the comma after a
	string literal to be optional in a format.  Use gfc_notify_std to
	issue an error/warning as appropriate.

	* io/format.c (parse_format_list): Allow the comma after a string
	literal to be optional.

From-SVN: r82109