*: 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/pimd/pim_signals.c b/pimd/pim_signals.c
index d1350b0..dcf4922 100644
--- a/pimd/pim_signals.c
+++ b/pimd/pim_signals.c
@@ -20,9 +20,10 @@
   $QuaggaId: $Format:%an, %ai, %h$ $
 */
 
+#include <zebra.h>
+
 #include <signal.h>
 
-#include <zebra.h>
 #include "sigevent.h"
 #include "memory.h"
 #include "log.h"