(enum attrs): Add A_FORMAT_ARG.

(enum attrs): Add A_FORMAT_ARG.

(init_attribute): Initialize it.
(decl_attributes, case A_FORMAT): Clean up error messages.
(decl_attributes, case A_FORMAT_ARG): New case.
(struct international_format_info): New structure and typedef.
(international_format_list): New variable.
(record_international_format): New function.
(init_format_info): Call it for gettext, dcgettext, and dcgettext.
(check_format_info): See if format arg is call to internationalization
function.

From-SVN: r12241