Compile_error_with_GHC_prerelease.mdwn

For various reasons we cannot use v8.0 (prereleases) yet,
but GHC v7.11.20150407

There was a compilation hiccup with polymorphic types. I corrected it in

https://github.com/ggreif/git-annex/tree/patch-1

The commit is

https://github.com/ggreif/git-annex/commit/a0ddad8d395b5eb61d1e7e6fdcbfa766c05de3d4

Cheers,

   Gabor

> Applied, thanks. [[done]] --[[Joey]]