*: 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/spacyc.c b/isisd/topology/spacyc.c
index 8531447..91a4799 100644
--- a/isisd/topology/spacyc.c
+++ b/isisd/topology/spacyc.c
@@ -1,3 +1,4 @@
+#include <zebra.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>