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

[Christian Maeder]

Simon Marlow wrote:
> As far as I can see, you don't need a package with a variant license in
> order to do what you want.  The package in question just has an option
> to use editline instead of readline at build-time.

I'm not the license expert. I did not invent a "variant license". GPL
seems to be fine for me in all cases.

> If you want to make life even easier, do as was suggested before and add
> a module with a single compatible API to both editline and readline, so
> clients can use the same API regardless of which package they link against.

Currently, I'm happy with Rob Dockins's Shellac-compatline.

>> You also abstract the choice between windows and unix. Doesn't that have
>> license implications, too?
> 
> I'm not aware of any license implications - what problem specifically
> are you referring to?

No specific problem. Can I freely link against all the window dlls
regarding file access (and thus for the Prelude) of package win32?

Cheers Christian