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superceded by the standard: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_udf b/openflow_input/bsn_udf
index f7ce9a6..12ad1cb 100644
--- a/openflow_input/bsn_udf
+++ b/openflow_input/bsn_udf
@@ -30,6 +30,7 @@
 
 #version 3
 #version 4
+#version 5
 
 /*
  * User Defined Fields