Pixmaps are reference counted and DestroyPixmap is called for the
removal of every reference. However, we only want to stop the adaptors
writing into the Pixmap just before the Pixmap is finally destroyed,
similar to how Windows are handled.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>