Migrate more of Data.Functor.* from transformers to base.

This was proposed in https://mail.haskell.org/pipermail/libraries/2015-July/026014.html

Edward says the following modules are up for migration:

• Data.Functor.Classes
• Data.Functor.Product
• Data.Functor.Sum
• Data.Functor.Compose

related/optionally/undecided:

• Data.Functor.Reverse
• Control.Applicative.Backwards

not moved because redundant (c.f. Const):

• Data.Functor.Constant

Trac metadata

Trac field	Value
Version	7.10.2
Type	Task
TypeOfFailure	OtherFailure
Priority	highest
Resolution	Unresolved
Component	libraries/base
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ekmett
Operating system
Architecture