bgpd: implement "next-hop-self all"

As specified in:
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/command/irg-cr-book/bgp-m1.html#wp4972925610

This allows overriding next-hop for ibgp learned routes on an
RR for reflected routes.

Especially useful for using iBGP in DMVPN setups. See:
http://blog.ipspace.net/2014/04/changes-in-ibgp-next-hop-processing.html

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
diff --git a/bgpd/bgpd.h b/bgpd/bgpd.h
index a1b1273..eae803d 100644
--- a/bgpd/bgpd.h
+++ b/bgpd/bgpd.h
@@ -412,6 +412,7 @@
 #define PEER_FLAG_MAX_PREFIX                (1 << 14) /* maximum prefix */
 #define PEER_FLAG_MAX_PREFIX_WARNING        (1 << 15) /* maximum prefix warning-only */
 #define PEER_FLAG_NEXTHOP_LOCAL_UNCHANGED   (1 << 16) /* leave link-local nexthop unchanged */
+#define PEER_FLAG_NEXTHOP_SELF_ALL          (1 << 17) /* next-hop-self all */
 
   /* MD5 password */
   char *password;