[zebra] linux policy routing support with ipv6

Quagga support linux policy routing (ip route ... table $X) with zebra.conf
table $X option.  It works fine on ipv4.  On ipv6 the parameter is ignored
(table 0 is used).

* zebra/...: Pass appropriate table arg to rib_{add,delete}_ipv6
diff --git a/zebra/rt_netlink.c b/zebra/rt_netlink.c
index 03df28c..7652f80 100644
--- a/zebra/rt_netlink.c
+++ b/zebra/rt_netlink.c
@@ -889,9 +889,9 @@
         }
 
       if (h->nlmsg_type == RTM_NEWROUTE)
-        rib_add_ipv6 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, 0, 0, 0);
+        rib_add_ipv6 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, table, 0, 0);
       else
-        rib_delete_ipv6 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, 0);
+        rib_delete_ipv6 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, table);
     }
 #endif /* HAVE_IPV6 */