common: Improve compare_string_versions.
* common/stringhelp.c: Include limits.h. (compare_version_strings): Change semantics to behave like strcmp. Include the patch lebel in the comparison. Allow checking a single version string. * common/t-stringhelp.c (test_compare_version_strings): Adjust test vectors and a few new vectors. * g10/call-agent.c (warn_version_mismatch): Adjust to new sematics. * g10/call-dirmngr.c (warn_version_mismatch): Ditto. * sm/call-agent.c (warn_version_mismatch): Ditto. * sm/call-dirmngr.c (warn_version_mismatch): Ditto.
- Signed-off-by: Werner Koch <wk@gnupg.org>