Compile IPA modules with C11 extensions

- define __STDC_WANT_LIB_EXT1__ to get C11 extensions like memset_s() for
  Samba's ZERO_STRUCT() macro, see
  https://en.cppreference.com/w/c/string/byte/memset
- _DEFAULT_SOURCE enables features like htole16() from endian.h, see
  http://man7.org/linux/man-pages/man3/endian.3.html
- _POSIX_C_SOURCE >= 200809 enables features like strndup() from string.h,
  see http://man7.org/linux/man-pages/man3/strndup.3.html
- time_t is no longer implicitly defined, include time.h
- typeof() is only available as GNU extension. Use explicit types
  instead of generic __typeof__().

Fixes: https://pagure.io/freeipa/issue/7858
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

util/ipa_krb5.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <time.h>
 #include <lber.h>
 #include <krb5/krb5.h>
 #include <kdb.h>