*: 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/isisd/topology/random.c b/isisd/topology/random.c
index c49c082..2c457c5 100644
--- a/isisd/topology/random.c
+++ b/isisd/topology/random.c
@@ -7,6 +7,7 @@
 /*                                                                   */
 /*********************************************************************/
 
+#include <zebra.h>
 #include <sys/types.h>
 #include <sys/times.h>