Small Cabal documentation patch: describe syntax of 'compiler' fields in .cabal files

[Duncan Coutts]

On Wed, 2009-06-10 at 15:52 -0400, Brent Yorgey wrote:
> Hi all,
> 
> When working on a .cabal file recently I couldn't find anything in the
> documentation about the proper syntax for the 'tested-with' field, so
> here's a patch to add a description of it to the documentation.

Applied, ta.

Duncan