sms: Add a script to query for unsent SMS

This is generating the query statement. It can be used to
play with database indexes and such.

openbsc/contrib/sms/hlr-query.st

@@ -0,0 +1,10 @@
+"Query for one SMS"
+
+Eval [
+1 to: 100 do: [:each |
+    Transcript show: 'SELECT SMS.* FROM SMS
+                        JOIN Subscriber ON SMS.receiver_id = Subscriber.id
+                            WHERE SMS.id >= 1 AND SMS.sent IS NULL AND Subscriber.lac > 0
+                            ORDER BY SMS.id LIMIT 1;'; nl.
+].
+]