b892f72
Do not define _GNU_SOURCE Let autotools to detect gnu features. Patch also prefer AC_USE_SYSTEM_EXTENSIONS to deprecated AC_GNU_SOURCE https://www.gnu.org/software/autoconf/manual/autoconf-2.67/html_node/Obsolete-Macros.html#index-AC_005fGNU_005fSOURCE-1960 Reviewed-by: Michal Židek <mzidek@redhat.com> Merges: https://pagure.io/SSSD/ding-libs/pull-request/3179