*: make sure zebra.h is always included first

zebra.h pulls in config.h, which results in fiddling with things like
__FILE_OFFSET_BITS. It must always be included first, in order to set
flags that influence the compiler via <features.h>.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/tests/test-timer-performance.c b/tests/test-timer-performance.c
index a529a5c..ee45ede 100644
--- a/tests/test-timer-performance.c
+++ b/tests/test-timer-performance.c
@@ -22,11 +22,12 @@
  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  * 02111-1307, USA.
  */
-#include <stdio.h>
-#include <unistd.h>
 
 #include <zebra.h>
 
+#include <stdio.h>
+#include <unistd.h>
+
 #include "thread.h"
 #include "pqueue.h"
 #include "prng.h"