fix haddock markup

Haddock dislikes lines with '{- #///' and has special treatment for it.

> Haddock coverage:
>    0% (  0 /  1) in 'Bindings.Libgit2.Windows'
>    0% (  0 /  1) in 'Bindings.Libgit2.Version'
>    0% (  0 / 17) in 'Bindings.Libgit2.Common'
>    0% (  0 / 50) in 'Bindings.Libgit2.Errors'
>    0% (  0 /  3) in 'Bindings.Libgit2.Message'
>    0% (  0 /  8) in 'Bindings.Libgit2.Strarray'
>    0% (  0 /  5) in 'Bindings.Libgit2.Threads'
>
> Bindings/Libgit2/Types.hsc:39:1: parse error on input `{'

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>