LLVM 3.5 rebase

[Adam Jackson]

Yep, this again.  I'm just as thrilled as you are.  3.5 is necessary for
proper ppc64le support, as well as some minor radeonsi features in Mesa.

One problem this time around appears to be python-llvmpy, which appears
to have decided that llvm 3.2/3.3 are the only versions it will support:

https://github.com/llvmpy/llvmpy/commit/1e141931b874dd0bc3d8e9d801b949939430ad4e

We're already shipping it built against 3.4, so that's truly charming.
I'm open to suggestions here.

- ajax