update to 2013Q1 Intel Graphics Stack Release

This changeset updates to all of the versions in
https://01.org/linuxgraphics/downloads/2013/2013q1-intel-graphics-stack-release
(but does not regression from newer version).

I tried generating 'servers/x11/xorg/default.nix' with the perl script,
but unrelated packges changed, so I just manually updated the file.
xf86-video-intel-2.21.7
fix url and hash for intel x driver
Merge pull request #556 from jcumming/x-updates.130523

update Intel Graphics Stack Release