[Yhc] - Bytecode library

Hi, I did some work on a byte code reader in Haskell, its going to form the basis of a bytecode API in the future [http://www.haskell.org/hawiki/Yhc/ByteCodeApi], but I'm not going to have that much time to do that in the near future, so here is what i have now. It can parse a single bytecode file, but only has the instructions decoded that I actually ended up using - thats easy enough to fix. Thanks Neil