*: add missing includes

Some places, particularly headers, were spewing warnings since they
don't include neccessary other headers to get struct/enum definitions.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/ospf6d/ospf6_neighbor.c b/ospf6d/ospf6_neighbor.c
index f20c83b..4e63797 100644
--- a/ospf6d/ospf6_neighbor.c
+++ b/ospf6d/ospf6_neighbor.c
@@ -38,6 +38,7 @@
 #include "ospf6_neighbor.h"
 #include "ospf6_intra.h"
 #include "ospf6_flood.h"
+#include "ospf6_snmp.h"
 #include "ospf6d.h"
 
 unsigned char conf_debug_ospf6_neighbor = 0;