[Haddock] DocTest integration into Haddock

[Simon Hengel]

Hi David,
thanks for your mail.  I almost missed it because my procmail sorted it
under 'haddock' due to the CC.

> I've applied the patch and done some refactoring after you got me
> thinking about the names of things. I renamed the original
> createInterfaces into processModules as it actually returns not only
> Interfaces but also the linking environment. Your function is now:
> 
>   createInterfaces :: [Flag] -> [String] -> IO [Interface]
> 
> I prefer Flag over raw command line strings since reader of the
> documentation can go to the Flag type to see which flags are actually
> accepted.

I have just adopted DocTest[1] to use that, and it works fine :)

Cheers,
Simon

[1] http://code.haskell.org/~sih/code/DocTest.git/