examples: include config.h

Since gnulib commit 6954995d unistd.h is included via stdlib.h
on BSD systems, which requires config.h to be included first.

Add config.h to the files that use it.

Part of this commit reverts commit 6ee918deSigned-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

examples/admin/client_close.c

+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <libvirt/libvirt.h>

examples/admin/client_info.c

-#define _GNU_SOURCE
+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>

examples/admin/client_limits.c

+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <libvirt/libvirt-admin.h>

examples/admin/list_clients.c

+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>

examples/admin/list_servers.c

+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <libvirt/libvirt-admin.h>

examples/admin/logging.c

+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
 
-#include "config.h"
 #include <unistd.h>
 #include <libvirt/libvirt-admin.h>
 #include <libvirt/virterror.h>

examples/admin/threadpool_params.c

+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <libvirt/libvirt-admin.h>

examples/dommigrate/dommigrate.c

@@ -20,6 +20,8 @@
  * <http://www.gnu.org/licenses/>.
  */
 
+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <libvirt/libvirt.h>

examples/hellolibvirt/hellolibvirt.c

@@ -2,6 +2,8 @@
  * hypervisor and gather a few bits of information about domains.
  * Similar API's exist for storage pools, networks, and interfaces. */
 
+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <libvirt/libvirt.h>

examples/openauth/openauth.c

 /* This is a copy of the hellolibvirt example demonstaring how to use
  * virConnectOpenAuth with a custom auth callback */
 
+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

examples/rename/rename.c

@@ -16,6 +16,8 @@
  * <http://www.gnu.org/licenses/>.
  */
 
+#include <config.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <libvirt/libvirt.h>