PR ld/6430

        PR ld/6430
            * testsuite/ld-elfcomm/elfcomm.exp (test_sort_common): Test the
            ascending/descending argument to the --sort-common command line
            option.
            * testsuite/ld-elfcomm/sort-common.s: New file.
            * ld.h (enum sort_order): New.
            * ldlang.c (lang_check: Fix comment.
            (lang_common): Sort commons in ascending or descending order.
            (lang_one_common): Likewise.
            * lexsup.c (ld_options): Have --sort-common take an option
            argument.
            (parse_args): Handle argument to --sort-common.
            * ld.texinfo (--sort-common): Document new optional argument.
            * NEWS: Mention new feature.