Thread affinity and wl_display_iterate

[Jørgen Lind]

Hi guys,

We have had a patch in Qt-Wayland since November that has given us some
thread affinity to Wayland clients so we can assure that we don't run
wl_display_iterate from other threads then the thread that actually created the
display. I have just cleaned it up a bit and was hoping to get it in
upstream. I also made up a quick patch to fix up the wayland gallium
backend. Should be pretty easy to fix the dri2 backend as well.

Jørgen