CVE-2020-25721 mitigation: KDC must provide the new PAC_REQUESTER_SID buffer with ObjectSID value associated with the requester's principal. The mitigation only works if NDR library supports the PAC_REQUESTER_SID buffer type. In case we cannot detect it at compile time, a warning will be displayed at configure stage. Fixes: https://pagure.io/freeipa/issue/9031 Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com> Reviewed-by: Rob Crittenden <rcritten@redhat.com> Reviewed-By: Rob Crittenden <rcritten@redhat.com>