*: 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/sprand.c b/isisd/topology/sprand.c
index 28b58b3..1c1eb19 100644
--- a/isisd/topology/sprand.c
+++ b/isisd/topology/sprand.c
@@ -1,3 +1,5 @@
+#include <zebra.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>