Destroy extended surface object

QWaylandExtendedSurface did not destroy for the corresponding wayland
object when deleted.

Change-Id: I8bd916b3c4d06d2727cf1718fd0daa84590ab7bd
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Change setDirectRenderSurface to return the result

No need to hide the bool; it can be useful in compositors to check if
direct rendering was properly activated.

Change-Id: I4c12c9719aa6b7b5ec4a91602c5052b6841e1780
Reviewed-by: Jan Arne Petersen <jan.petersen@kdab.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>