Make alert notifications vty configurable per ESME

Adds (no) alert-notifications as a per-esme vty command,
in order to allow some ESMEs to be excluded from alerts.

The default is still to send alert notifications to all esme,
so no changes are required to the config file to maintain
identical operation after this patch.

Change-Id: I57f4d268ca6fe6a233f2caaffce62e4aade01274
diff --git a/src/libmsc/smpp_smsc.h b/src/libmsc/smpp_smsc.h
index 27a2646..dc7b7c1 100644
--- a/src/libmsc/smpp_smsc.h
+++ b/src/libmsc/smpp_smsc.h
@@ -68,6 +68,7 @@
 	int deliver_src_imsi;
 	int osmocom_ext;
 	int dcs_transparent;
+	int alert_notifications;
 	struct llist_head route_list;
 };