Bump MODULE_VERSION to 5.2.1

Change-Id: Iee840bb9cf19e8aeb219dd579ad75595270e407e
Reviewed-by: Matti Paaso <matti.paaso@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Merge remote-tracking branch 'origin/stable' into dev

Conflicts:
	.qmake.conf

Change-Id: Icab7fb1dd11851639a46b2cb211ded5df92a1dbe