Add VTY command to specify default speech codec

In order to have the MNCC application reliably decide on the codec type,
it needs to know if we are running on a TCH/F or TCH/H.  Thus, we pass
lchan_mode as a new parameter to the 'struct gsm_mncc'
diff --git a/openbsc/include/openbsc/mncc.h b/openbsc/include/openbsc/mncc.h
index ed1bfd6..8c59fe2 100644
--- a/openbsc/include/openbsc/mncc.h
+++ b/openbsc/include/openbsc/mncc.h
@@ -148,6 +148,7 @@
 	int		emergency;
 	char		imsi[16];
 
+	unsigned char	lchan_type;
 	unsigned char	lchan_mode;
 };