bgpd: store nexthop info for redistributed IPV6 routes

BGP was ignoring nexthop info for static and other redistributed
routes for IPv6.  Build extra attribute info to store the nexthop.
See also:
  https://bugzilla.vyatta.com/show_bug.cgi?id=6073
diff --git a/bgpd/bgp_route.h b/bgpd/bgp_route.h
index 3e52859..7adc573 100644
--- a/bgpd/bgp_route.h
+++ b/bgpd/bgp_route.h
@@ -192,7 +192,9 @@
 
 extern int bgp_maximum_prefix_overflow (struct peer *, afi_t, safi_t, int);
 
-extern void bgp_redistribute_add (struct prefix *, struct in_addr *, u_int32_t, u_char);
+extern void bgp_redistribute_add (struct prefix *, const struct in_addr *,
+				  const struct in6_addr *,
+				  u_int32_t, u_char);
 extern void bgp_redistribute_delete (struct prefix *, u_char);
 extern void bgp_redistribute_withdraw (struct bgp *, afi_t, int);