The Display provides a method to create the shm pool and a
BufferInterface class is added to the server module. It is created
from the SurfaceInterface when a buffer gets attached to the surface.
The BufferInterface can be referenced and once its unreferenced it
sends a buffer release to the client and destroys itself.
For the case that the buffer is a shm buffer the BufferInterface
provides a convenience method to turn it into a QImage.
The auto test for Surface is extended by attaching buffers to the
surface and verifying that the content is correct.
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