Object file loading on Windows

The CPU backend is currently broken on windows because it lacks an object file loader (here).

This is the same as what GHCi does, but a bit simpler because we only need to handle the most basic types of relocations etc. Unfortunately we can't use that one due to GHC#13624 (unless that does not affect windows, but I doubt it)

Any windows hackers interested in writing one? @RyanGlScott