[Yhc] Killing off nhc

[Neil Mitchell]

Hi

> Sorta kinda.  Yhc uses MTL (afair), which uses undecidable instances to
> implement a feature Yhc doesn't use.  Somebody really ought to split up
> MTL, but there doesn't seem to be an easy way for people without direct
> access to split packages...

Ross is doing that, there will soon be mtl-extras and mtl-base. As it
stands, nhc already has mtl, just not the bits that Yhc doesn't use. I
doubt mtl will give us much hassle.

Thanks

Neil