fixes llvm 3.6 build due to recent api changes

See: https://github.com/llvm-mirror/llvm/commit/548f2b6e8fc5499fa8c9394fe7d110f50c487802
I know, my changes to llvm were reverted. See https://github.com/JuliaLang/julia/issues/7910. I'm working on fixing this, but there's so amount of work left to be done.