proposed change to transformers package

[Ross Paterson]

I propose to rename some of the modules in the transformers package so
that it no longer conflicts with the mtl package:

  Control.Monad.Identity renamed as Data.Functor.Identity
  Control.Monad.Trans split between Control.Monad.Trans.Class and
        Control.IO.Trans.Class

Then Control.Monad.Identity and Control.Monad.Trans are added to monads-fd
making it closer to mtl.  Darcs repositories:

  http://code.haskell.org/~ross/transformers/
  http://code.haskell.org/~ross/monads-fd/

Docs:

  http://code.haskell.org/~ross/transformers/dist/doc/html/transformers/
  http://code.haskell.org/~ross/monads-fd/dist/doc/html/monads-fd/