GHC 7.8.1: Many haddock-related complaints from 'ghc-pkg check'

[Herbert Valerio Riedel]

On 2014-04-09 at 19:53:47 +0200, Conal Elliott wrote:
> From a bit of experimentation, it appears that the problematic packages do
> indeed have Haddock failures. For instance,
>
>     bash-3.2$ cd random-1.0.1.1/
>     bash-3.2$ cabal configure
>     Resolving dependencies...
>     Configuring random-1.0.1.1...
>     bash-3.2$ cabal haddock
>     Running Haddock for random-1.0.1.1...
>     Preprocessing library random-1.0.1.1...
>     Haddock coverage:
>
>     System/Random.hs:2:2: parse error on input '#'

Fyi, this one specifically looks as if it could be related to

 https://github.com/haskell/cabal/issues/1740#issuecomment-39559026

I.e. caused by `clang -E` not being "semi-idempotent" (meaning the
result from the second CPP pass can't be parsed anymore by GHC)