Add missing comparison operators

Change-Id: I14c8b03602559822b1e7b9c1d26515c619cf1ae8
Reviewed-by: Michael Krasnyk <michael.krasnyk@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>