Update xf86-video-ati to 7.7.0.

I'm pleased to announce the 7.7.0 release of xf86-video-ati, the Xorg
driver for ATI/AMD Radeon GPUs supported by the radeon kernel driver.
This release supports xserver versions 1.9-1.18.

Highlights:

* Option "TearFree" can now prevent tearing with rotation/reflection as
  well (with Xorg >= 1.16).
* RandR CRTC transforms now work correctly (but for now still exhibit
  tearing even with TearFree).
* The RandR 1.4 provider name is now no longer hardcoded to "radeon"
  but constructed from the GPU chipset name and bus ID, allowing
  several GPUs supported by this driver to be distinguished by name.
* The RandR primary output is now always explicitly marked as such.
* The driver can now make use of more than 256MB of VRAM for scanout
  buffers, allowing e.g. virtual desktop sizes >= 8192x8192 to work.
* The driver can prevent clients trying to use the DRI3 extension over a
  display connection forwarded via SSH from hanging.
* Many more fixes for issues using the DRI3/Present extensions.

Plus many other small improvements and fixes. Thanks to everybody who
contributed to this release in any way!


(wiz)