Bump MODULE_VERSION to 5.2.1

Change-Id: Ic460fc350c446a91ef105b7fe92cda937f0ef914
Reviewed-by: Matti Paaso <matti.paaso@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Simo Fält <simo.falt@digia.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: Ie268c1b4ad0e49393015d3a1a46785bb8c17c44a