[bgpd] AS4 bugfix by Chris Caputo <ccaputo@alt.net>

* bgpd/bgp_aspath.c: (aspath_make_str_count) "assert (len < str_size)" was
  getting hit under certain 4-byte ASN conditions. New realloc strategy.
* bgpd/bgp_aspath.c: (aspath_key_make) const warning fix.

"%d" -> "%u" 4-byte ASN corrections.  Prevent negative number when ASN is
above 2^31.
diff --git a/bgpd/bgp_community.c b/bgpd/bgp_community.c
index 1cafdb3..a05ea6c 100644
--- a/bgpd/bgp_community.c
+++ b/bgpd/bgp_community.c
@@ -282,7 +282,7 @@
 	default:
 	  as = (comval >> 16) & 0xFFFF;
 	  val = comval & 0xFFFF;
-	  sprintf (pnt, "%d:%d", as, val);
+	  sprintf (pnt, "%u:%d", as, val);
 	  pnt += strlen (pnt);
 	  break;
 	}