Add SGs Interface

Add an SGs interface (3GPP TS 29.118) to osmo-msc in order to support
SMS tunneling and Circuit Switched Fallback (CSFB)

Change-Id: I73359925fc1ca72b33a1466e6ac41307f2f0b11d
Related: OS#3615
diff --git a/src/libmsc/gsm_09_11.c b/src/libmsc/gsm_09_11.c
index 608d4ff..dca315d 100644
--- a/src/libmsc/gsm_09_11.c
+++ b/src/libmsc/gsm_09_11.c
@@ -343,7 +343,8 @@
 
 	/* Trigger Paging Request */
 	trans->paging_request = subscr_request_conn(vsub,
-		&handle_paging_event, trans, "GSM 09.11 SS/USSD");
+		&handle_paging_event, trans, "GSM 09.11 SS/USSD",
+	        SGSAP_SERV_IND_CS_CALL);
 	if (!trans->paging_request) {
 		LOGP(DMM, LOGL_ERROR, "Failed to allocate paging token\n");
 		trans_free(trans);