llvm: update 3.3 -> 3.4

- Drop a patch that no longer applies: the default limit got tripled,
  so I hope it's sufficient now anyway.
- R600 support is no longer experimental and enabled by default.
- A few packages haven't been ported to 3.4 by upstream yet,
  so I will probably re-introduce 3.3 for them
  (so we can merge to master sooner).
mesa: update to 10.0.1, always enable R600

A few TODOs are pending, but of relatively low importance.
xorg: update a few sub-packages
xf86-video-vmware: xatracker2 patch to build with mesa 10
Merge master into x-updates
mesa: bugfix update 10.0.1 -> .2
Merge master into x-updates

Llvm refactorings from ae0c9b626f5 included.
Mesa is the only package using llvm_34 ATM.

Conflicts:
	pkgs/development/compilers/llvm/default.nix
harfbuzz: update from 0.9.24 to 0.9.25

I see no significant change in the changelog.
mesa: keep llvm versioning outside of expression file
Merge master into x-updates

Conflicts (re-created on master, preserved):
	pkgs/development/compilers/llvm/3.3/more-memory-for-bugpoint.patch
libusb1: name it libusbx, so it's more clear
Merge separate branches, both on x-updates
mesa: try enabling checkPhase again
Revert "mesa: try enabling checkPhase again"

I'm getting something like https://bugs.freedesktop.org/show_bug.cgi?id=52136

This reverts commit 5674fb556b97311a0f1fbdfafa73b85a3edec4cb.
mesa: fix build by adding ncurses

After stdenv merge it seems needed, and drivers remain linked against it.

Tests still don't link.
Merge master into x-updates
xorg: move nouveau driver here, some updates of modules

It seems that most of the modules is rarely used, but still.

Some of the updated modules don't build, just as they didn't before.
Merge master into x-updates
mesa cleanup: remove patches, clean description

werror-wundef.patch came from #1082, but now no longer applied,
and it seems no longer necessary, as both qt5 and qtCreator build.
@bbenoist: was the patch useful for anything else?
Merge master into x-updates (to fix qt5 build)