WIP: linux patchset

Oh good, now I can segfault in Qt! :smile:. I figured it makes more sense to just open this as a wip until it works and then refine it to something mergeable.

further changes from last night:
- another missing `libcxxffi` in an eval'd ccall definition
- `RTLD_GLOBAL` for the Qt libs

in Julia I also did:
- `extern "C" void *cjulia_type_to_llvm(jl_value_t* jt) { return (void*) julia_type_to_llvm(jt); }` because that function is otherwise C++ mangled, so could not be found (I take it the Apple linker's search heuristic is approximately *"ohhaiguyz i see you r luking for that private mangled function? heh, s'cool here ya go"*)