Bump MODULE_VERSION to 5.2.1

Change-Id: I59276a6546747fb7e5e73fba25f199936884a828
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: I194516b948b437c85f0c6f93a1b0b339a4a76bb9