[PATCH 00/14] Various fixes

[Adam Jackson]

Resends of a bunch of stuff.  The first three disable extensions that
currently don't work when Xinerama is active.  4 fixes the scheduler timings
to be plausible for actually making 60fps reliably.  5 through 7 are various
buglets in backing store, most importantly making it Just Work when Composite
is enabled since Composite is how it's implemented.  8 is a fallback ordering
fix that's useful for UEFI machines (though, yes, vesa's probe is still worth
fixing).  And the rest fix enough of the fixes/damage/composite stack to make
it actually work when xinerama is enabled.

#8 is reviewed, the rest inexplicably aren't yet.  In particular, hey KDE,
those last six make your Render backend for kwin compositing actually work
across multiple GPUs, maybe you think this would be nice to have?  And I'm
told if you're using NVIDIA's driver even gnome-shell works (assuming you
rebase those last 6 back to 1.14.x).

The last two are modified from previous versions to only touch the root
window.  I managed to convince myself that the affected regions are in
fact drawable-relative, which means only root windows need to be fixed;
normal windows will have the right thing done to them in the process of
translating them to screen coordinates.  Render's SetPictureClipRectangles
is still broken for this case, but a) not new and b) not breaking any app
I happen to care about at the moment.

- ajax