BUILD: Add version symbol files for public libraries. Version symbol files will help package systems to catch backward compatible changes (newly added functions) into library. The difference between libraries libsss_nss_idmap_test.so and libsss_nss_idmap.so is that the 1st library will not be installed and has more exported functions, which are necessary for mocking with cmocka for test sss_nss_idmap-test. Resolves: https://fedorahosted.org/sssd/ticket/2194 Reviewed-by: Sumit Bose <sbose@redhat.com> Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>