glamor: pull in fixes from git

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
xf86-video-ati: add 7.3.0_git recipe

the 7.3.0 update contains a lot of improvements when using glamor
0.6.0+.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>