[bgpd] add comment that bgp_capability_receive is exported for unit-tests
diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index de02bb8..d98b689 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -2208,7 +2208,10 @@
   return 0;
 }
 
-/* Dynamic Capability is received. */
+/* Dynamic Capability is received. 
+ *
+ * This is exported for unit-test purposes
+ */
 int
 bgp_capability_receive (struct peer *peer, bgp_size_t size)
 {