Add Functor/Applicative instances for all Monads in GHC

[David Luposchainsky]

Hello GHC devs,

due to the formation of the Haskell Prime Committee [1], I am motivated
to propose another go at the "Applicative => Monad" issue. Regardless of
the future of that proposal, I think some changes required by it are
beneficial in any case, namely ensuring that all Monads defined in GHC
get Applicative/Functor instances.

I've successfully modified toy version of 7.6.3 to include these
instances to see how it goes, and as you can imagine the changes are
numerous but simple; I don't assume HEAD won't be much different in that
respect.

However, since this would by my first involvement in a project as large
as GHC, I am not quite sure of the procedure to follow, even after
reading the corresponding Trac/Wiki pages. I'm assuming the policy here
is the same as for the libraries mailing list (hence this email), and
upon positive feedback I can open a Trac issue, take ownership, clone,
modify, send pull request etc. If there's anything wrong with that
approach here please tell me.

Greetings,
David


[1] http://thread.gmane.org/gmane.comp.lang.haskell.general/19796