sort: new option, --sort=version, for version number ordering

sort: new option, --sort=version, for version number ordering

* src/sort.c [struct keyfield] (version): New member.
(usage): Describe --version-sort.
(sort_options): Add 'V'.
(long_options): Add "version-sort".
(CHECK_TABLE, _ct_, SORT_TABLE, _st_): Define new macros.
(check_args, sort_args, sort_types): Use these new macros in declarations.
(ARGMATCH_VERIFY): Remove use.  No longer needed.
(compare_version): New function.
(key_compare): Add a case.
(check_ordering_compatibility): Handle new type.
(main): Likewise.  Reformat two expressions for readability.
* tests/misc/sort-version: new test file
* tests/Makefile.am: add it to the list
* doc/coreutils.texi (sort invocation): Document it.
* NEWS: Mention the new feature.