Location service: toggle the service from the main menu

That way we don't track the user's location until explicitly asked to do
so.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-mobile/gpslocation.h

@@ -20,6 +20,7 @@ private:
 signals:
 
 public slots:
+	void serviceEnable(bool toggle);
 	void newPosition(QGeoPositionInfo pos);
 	void updateTimeout();
 };