xf86-video-ati page flipping fixes

[Ville Syrjala]

I came to the conclusion that the xserver DRI2 invalidate patches that
have been discussed aren't really fixing the problem. I suppose they may
make the problem slightly less likely to happen, but at least for me that
likelyhood is still very high. The whole mess looks like a simple driver
bug to me.

These patches make unredirecting fullscreen windows w/ compiz + page
flipping work a lot better for me. I've still seen an occasional complain
from the kernel [1] and one time the kernel went into some infinite page
fault loop, printing stuff endlessly to the console, but other than those
things seem much more solid now.

[1] [drm:radeon_crtc_page_flip] *ERROR* failed to reserve new rbo buffer before flip