* listing.c: Add -ag listing flag to show general information in

    * listing.c: Add -ag listing flag to show general information in
        listings such as gas version, passed options, and time stamp.
        (listing_general_info): New function.
        (print_options): New function.
        (print_single_option): New function.
        (print_timestamp): New function.
        (MAX_DATELEN): Define.
        (listing_print): Add call to listing_general_info.
        * listing.h (LISTING_GENERAL): Define.
        (listing_print): Add new parameter.
        * as.c (show_usage): Print new switch.
        (parse_args): Parse new switch.
        (main): Pass command line on to listing_print.
        * NEWS: Mention this new feature.
        * doc/as.texinfo: Document the new sub-option.

        * gas/all/gas.exp: Check the performance of the -ag command line
        switch.