Wayland compatibility layer

[Po Lu]

Over the past several months, I and some other individuals wrote a
Wayland compositor that runs on common X setups.  The code can be found
here:

  https://sourceforge.net/projects/twelveto11/

It should be a more or less complete implementation of the important
parts of the Wayland protocol.  Buffer transforms are currently missing,
but that's because I can't wrap my head around how they work.  If DRI3
is extended to allow creating Xv video, it would allow implementing YUV
image formats without a dependency on GL.

The only major inefficiency I can think of is that buffer contents get
copied at least once, to the offscreen storage of the toplevel window,
which is then composited by the X compositing manager.  Buffer-flipping
does not yet work well for fullscreen opaque surfaces, as that requires
some additions to the Composite extension here to work well:

  https://lists.x.org/pipermail/xorg-devel/2022-October/058918.html

Please try it out and report any crashes or bugs that you may come
across.  Thanks in advance.  Patches are also welcome, and the code
should be well commented and structured, but please keep in mind the
coding standards (which happen to overlap greatly with the GNU ones):
https://www.gnu.org/prep/standards.