paging: Send SGsAP-SERVICE-ABORT-REQUEST on paging timeout

When pagig for a CS-Call via SGs times out, the MME expects to be
informed about this via an SGsAP-SERVICE-ABORT-REQUEST, make sure this
message is sent, but only for CS-Fallback calls.

Change-Id: I3f8f153afe24cf2efa245713509bdc8488902877
Depends: osmo-ttcn3-hacks I99950a17ccf26aaa0eebded5480f33be4c57586a
Related: OS#3614
diff --git a/include/osmocom/msc/sgs_iface.h b/include/osmocom/msc/sgs_iface.h
index 575468e..a319663 100644
--- a/include/osmocom/msc/sgs_iface.h
+++ b/include/osmocom/msc/sgs_iface.h
@@ -89,4 +89,5 @@
 int sgs_iface_tx_paging(struct vlr_subscr *vsub, enum sgsap_service_ind serv_ind);
 int sgs_iface_tx_dtap_ud(struct msc_a *msc_a, struct msgb *msg);
 void sgs_iface_tx_release(struct vlr_subscr *vsub);
+void sgs_iface_tx_serv_abrt(struct vlr_subscr *vsub);