bgpd: Enable support for BGP IPV6 multipath.

This commit adds these two commands:
maximum-paths <1-MULTIPATH_NUM>
maximum-paths ibgp <1-MULTIPATH_NUM>

under address-family ipv6 mode.  In addition adding the ability
to pass multiple paths down into zebra from bgp.

Signed-off-by: Ayan Banerjee <ayan@cumulusnetworks.com>
Signed-off-by: Dinesh G Dutt <ddutt@cumulusnetworks.com>
Reviewed-by: Scott Feldman <sfeldma@cumulusnetworks.com>
diff --git a/bgpd/bgp_zebra.h b/bgpd/bgp_zebra.h
index 2565158..ccc5547 100644
--- a/bgpd/bgp_zebra.h
+++ b/bgpd/bgp_zebra.h
@@ -22,9 +22,11 @@
 #define _QUAGGA_BGP_ZEBRA_H
 
 #define BGP_NEXTHOP_BUF_SIZE (8 * sizeof (struct in_addr *))
+#define BGP_IFINDICES_BUF_SIZE (8 * sizeof (unsigned int))
 
 extern struct stream *bgp_nexthop_buf;
 extern struct in_addr router_id_zebra;
+extern struct stream *bgp_ifindices_buf;
 
 extern void bgp_zebra_init (struct thread_master *master);
 extern void bgp_zebra_destroy (void);