patch applied (cabal): Revert the other `fmap` to (.)

[Ross Paterson]

On Thu, May 01, 2008 at 03:51:13PM +0100, Malcolm Wallace wrote:
> nhc98 has a performance hack to avoid dumping large numbers of instance
> decls into .hi interface files.  For any given instance, if both the
> class and the type are defined in the Prelude, then the instance can be
> omitted from the interface file (for any module except the Prelude
> itself), under the assumption that it will already be available by
> default via the Prelude, which is implicitly imported everywhere anyway.
> This assumption is entirely reasonable for H'98.
> 
> But non-H'98 modules that add new instances for Prelude types and
> classes break the assumption.

I don't think it is reasonable.  There is nothing in H98 that forbids
defining instances for Prelude types and classes, as long as they don't
get into modules defined in the H98 Report.  Open world and all that.