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/src/libmsc/gsm_04_08.c b/openbsc/src/libmsc/gsm_04_08.c
index dcb6e11..0cd707d 100644
--- a/openbsc/src/libmsc/gsm_04_08.c
+++ b/openbsc/src/libmsc/gsm_04_08.c
@@ -1839,6 +1839,8 @@
 
 	memset(&setup, 0, sizeof(struct gsm_mncc));
 	setup.callref = trans->callref;
+	if (trans->conn && trans->conn->lchan)
+		setup.lchan_type = trans->conn->lchan->type;
 	tlv_parse(&tp, &gsm48_att_tlvdef, gh->data, payload_len, 0, 0);
 	/* emergency setup is identified by msg_type */
 	if (msg_type == GSM48_MT_CC_EMERG_SETUP)
@@ -1995,6 +1997,8 @@
 
 	memset(&call_conf, 0, sizeof(struct gsm_mncc));
 	call_conf.callref = trans->callref;
+	if (trans->conn && trans->conn->lchan)
+		call_conf.lchan_type = trans->conn->lchan->type;
 	tlv_parse(&tp, &gsm48_att_tlvdef, gh->data, payload_len, 0, 0);
 #if 0
 	/* repeat */