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).