patch applied (packages/base): IsString is GHC-only (so why is it in the Prelude?)

[Simon Marlow]

Malcolm Wallace wrote:

> [ Actually, to be honest I'm not quite sure why the Prelude module lives
>   in the base package, rather than the haskell98 package?  The same
>   question applies to the Numeric module. ]

Packages don't support re-exposing modules from other packages right now; it has 
been suggested as an extension from time to time.  If we did have support for 
re-exposing then the haskell98 package could re-expose Prelude and Numeric, and 
it would be possible for a pure Haskell 98 program/library to depend only on the 
haskell98 package.

Right now we have the situation that a program/library can be independent of the 
haskell98 package, which wouldn't be true if Prelude were in haskell98.  Also it 
would make building base a bit harder, because nothing would be able to import 
Prelude.

Cheers,
	Simon