Bump MODULE_VERSION to 5.2.1

Change-Id: I0b407bf6ad77eadcde69683861db52ba76e2090c
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: I96adbf312c94e0f70ccc8d2b676155e1f79a56cb