patch applied (packages/mtl): use Control.Monad.Instances from base

[Ross Paterson]

On Wed, Apr 12, 2006 at 01:06:46AM +1000, Donald Bruce Stewart wrote:
> Oh, that reminds me. Something we've often talked about on #haskell.
> Should the (a -> ) monad in Control.Monad.Reader be moved into the
> base package, since its such a fundamental structure?
> 
> Its quite hard to find, which is annoying since lambdabot's refactoring
> tools use the (a ->) monad all over the place.
> 
> This guy:
>     instance Functor ((->) r) where
>         fmap = (.)
> 
>     instance Monad ((->) r) where
>         return  = const
>         m >>= k = \r -> k (m r) r

They're now in Control.Monad.Instances, as are the Functor instances for
(,) and Either.  The MonadFix instance is now in Control.Monad.Fix.