ospf6d: add SNMP notifications/traps support

Only implement ospfv3NbrStateChange and ospfv3IfStateChange.
diff --git a/ospf6d/ospf6_snmp.h b/ospf6d/ospf6_snmp.h
index 5c67893..fa1b0c3 100644
--- a/ospf6d/ospf6_snmp.h
+++ b/ospf6d/ospf6_snmp.h
@@ -22,6 +22,8 @@
 #ifndef OSPF6_SNMP_H
 #define OSPF6_SNMP_H
 
+extern void ospf6TrapNbrStateChange (struct ospf6_neighbor *);
+extern void ospf6TrapIfStateChange (struct ospf6_interface *);
 extern void ospf6_snmp_init (struct thread_master *);
 
 #endif /*OSPF6_SNMP_H*/