darcs patch: [PROOF OF CONCEPT] build readline package with libedit

[Henning Thielemann]

On Tue, 19 Feb 2008, Thomas Schilling wrote:

> I don't think Cabal can help easily here since it works on the module
> level.  It also won't rename modules which would be required in this
> case, I think.

You can separate the differences out in two modules with the same name but
different source directories and add a Cabal switch on a flag that chooses
between two Hs-Source-Dirs.