Prevent crash when extended surface is destroyed.

The surface is not destroyed synchronously with the extended surface
so there is a small chance that something accesses
Surface::extendedSurface() between the time when the extended
surface is destroyed and the Surface itself is cleaned up.

We also want to make sure that the extended surface is not hanging
around after the surface is destroyed, so nuke it immediately on
surface_destroy_resource.

Change-Id: I87eff0b07727f1b528e803a5a617908658665f20
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Initialize 'm_visibility' member variable

Change-Id: I638feb828792257ecf7bd29c4f86ed2d06174590
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Set the right content orientation of the extended window on QWaylandWindow ctor

Change-Id: I5cf5afc7b920ff754fb21fc748af61a596e20c7b
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>