[DGD] zlib, mccp and dgd

[Shentino]

>
> If im on the right track...thanks for the discussion.
> chris
>
I was actually hoping that dworkin would implement this driver side,
and was about to suggest that until I saw the rejection, so you're on
the best track you can be on. :P  (j/k felix, there's probably
technical reasons)

Check out the driver source for the encrypt/decrypt kfuns and you'll
see a nice way to make a flexible kfuns to handle zlib, lzw, bzip,
bzip2, and so on.  Would be easier than writing separate kfuns for
each (I think there's an 8 bit limit on kfun specifiers).

I would be careful though.  IIRC, some compression algorithms work on
blocks instead of streams.  Be careful in that case and if there are
any block bounds to worry about make sure that you obey them.