Register WL_SHM_FORMAT_ARGB2101010 and its XRGB,ABGR, and XBGR variants.
These (little-endian) formats are only advertised on little endian
machines, where there exist matching (native-endian) QImage formats.
Currently, if an application is closed, all of its shm buffers will be
destroyed. However, the compositor may want to access them to fade out
the window.
With this change, the underlying shm pool will be referenced when a shm
buffer is destroyed. So, the compositor can access buffer data even if
the buffer is destroyed.
Currently, the BufferInterface encapsulates all the kinds of client
buffers. This has become a somewhat annoying issue as we want to
reference the shm pool if a shm buffer is destroyed, or have custom
buffer readiness logic for linux dma-buf client buffers.
Implementing all of that with the current abstractions will be
challenging as there's no good separation between different client
buffer types.
This change splits the BufferInterface class in three sub-classes -
DrmClientBuffer, LinuxDmaBufV1ClientBuffer, and ShmClientBuffer.
In addition to that, this change fixes the broken buffer ref'ing api.
