openflow_input: add BSN extensions to OF 1.4

I left out the following extensions that are no longer used or have been
superceded by the standard:

 - bsn_disable_split_horizon_check
 - bsn_role_status
 - bsn_global_vrf_allowed
diff --git a/openflow_input/bsn_tcp_flags b/openflow_input/bsn_tcp_flags
index e8ef2e9..1a84a90 100644
--- a/openflow_input/bsn_tcp_flags
+++ b/openflow_input/bsn_tcp_flags
@@ -30,6 +30,7 @@
 
 #version 3
 #version 4
+#version 5
 
 /*
  * TCP flags