fixes llvm 3.6 build due to recent api changes

See: https://github.com/llvm-mirror/llvm/commit/548f2b6e8fc5499fa8c9394fe7d110f50c487802
These changes build with the latest master of llvm, but backtraces seem to be broken.
```julia
julia> ccall(:jl_lookup_code_address, Any, (Ptr{Void},), 1)
error: failed to compute relocation: X86_64_RELOC_UNSIGNED
error: failed to compute relocation: X86_64_RELOC_UNSIGNED
error: failed to compute relocation: X86_64_RELOC_UNSIGNED
error: failed to compute relocation: X86_64_RELOC_UNSIGNED
(:anonymous,symbol("./no file"),0,false,1)
```