Docs for Haskell bindings: Add parameter names to type signatures

[tarleb]

Haddock allows to add a description to each type in a function signature, e.g.

example :: Int     -- ^ the foo number
        -> Double  -- ^ bar multiplier
        -> Maybe Double  -- ^ quux

Real-life rendering example.

I believe that this could help to improve the readability of the docs and would be happy to contribute a patch for this change. Please let me know if a PR would be welcome.