first 'working' SMS implementation

we now have the full path from the MS into the database (SUBMIT), as well as
back from the database to the MS (DELIVER).  The database gets correctly
updated once a SMS has been successfully delivered.

What's still missing is the periodic scan over all undelivered messages,
trying to deliver them to the respective MS.  So far, you have to manually
trigger this on the telnet interface with 'sms send pending 1'
diff --git a/openbsc/include/openbsc/signal.h b/openbsc/include/openbsc/signal.h
index 1b96a60..dea6344 100644
--- a/openbsc/include/openbsc/signal.h
+++ b/openbsc/include/openbsc/signal.h
@@ -46,6 +46,13 @@
 	S_PAGING_COMPLETED,
 };
 
+/* SS_SMS signals */
+enum signal_sms {
+	S_SMS_SUBMITTED,	/* A SMS has been successfully submitted to us */
+	S_SMS_DELIVERED,	/* A SMS has been successfully delivered to a MS */
+	S_SMS_SMMA,		/* A MS tells us it has more space available */
+};
+
 /* SS_ABISIP signals */
 enum signal_abisip {
 	S_ABISIP_BIND_ACK,