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>
Enable -Werror for all of qtsvg

Change-Id: Ica038c81648e3d3c7c2418aacf40eef1f62602b6
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Remove unused pmKey function

Found by Clang 3.4.

Change-Id: Ie4e9fc535ee44caae561aacdc245c64ea5b30b46
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>