lcr uses MNCC_SOCK_VERSION 5, but this is binary compatible to
what openbsc thinks is version 4.  The only difference is the added
RTP related commands, which are optional.

Index: openbsc/include/openbsc/mncc.h
===================================================================
--- openbsc.orig/include/openbsc/mncc.h
+++ openbsc/include/openbsc/mncc.h
@@ -163,7 +163,7 @@ struct gsm_data_frame {
 	unsigned char	data[0];
 };
 
-#define MNCC_SOCK_VERSION	4
+#define MNCC_SOCK_VERSION	5
 struct gsm_mncc_hello {
 	uint32_t	msg_type;
 	uint32_t	version;