db v4: add column last_lu_seen_ps

Location Updating procedures from both CS and PS overwrite the same
last_lu_seen field of a subscriber. For upcoming D-GSM it will be important to
distinguish those, because only CS attaches qualify for MSISDN lookup.

Add column last_lu_seen_ps, and upon PS LU, do not overwrite last_lu_seen, so
that last_lu_seen now only reflects CS LU.

In the VTY, dump both LU dates distinctively.

Change-Id: Id7fc50567211a0870ac0524f6dee94d4513781ba
diff --git a/sql/hlr.sql b/sql/hlr.sql
index f8fdc0b..ad57661 100644
--- a/sql/hlr.sql
+++ b/sql/hlr.sql
@@ -42,7 +42,8 @@
 
 	-- Timestamp of last location update seen from subscriber
 	-- The value is a string which encodes a UTC timestamp in granularity of seconds.
-	last_lu_seen TIMESTAMP default NULL
+	last_lu_seen TIMESTAMP default NULL,
+	last_lu_seen_ps TIMESTAMP default NULL
 );
 
 CREATE TABLE subscriber_apn (
@@ -77,4 +78,4 @@
 
 -- Set HLR database schema version number
 -- Note: This constant is currently duplicated in src/db.c and must be kept in sync!
-PRAGMA user_version = 3;
+PRAGMA user_version = 4;