ospf6d: implement 'match interface' for route-maps

ospf6_routemap_rule_match_interface* was imported from ospfd
daemon with minor changes. new CLI options defined.

`ospf6_routemap_rule_match_interface' was changed to support
IPv6 (ospfv3) route's external information.
diff --git a/ospf6d/ospf6_asbr.h b/ospf6d/ospf6_asbr.h
index db4561d..5f072cf 100644
--- a/ospf6d/ospf6_asbr.h
+++ b/ospf6d/ospf6_asbr.h
@@ -48,6 +48,8 @@
 
   struct in6_addr forwarding;
   /* u_int32_t tag; */
+
+  unsigned int ifindex;
 };
 
 /* AS-External-LSA */