Support Haddock for function arguments

[mruegenberg]

Often, the argument names in C headers serve as partial documentation.

Since Haskell function types lack names for arguments, it would be helpful if Haddocks in #fun definitions were put into the generated Haskell code.

---

An example C function:

`void foo(int width, int height);`

with the corresponding .chs:

{#fun foo
    { `Int' -- ^ width
    , `Int' -- ^ height
    } -> `()' #}

This should generate code like this:

foo :: (Int) -- ^ width
    -> (Int) -- ^ height 
    -> IO ()
foo a1 a2 =
  let {a1' = fromIntegral a1} in 
  let {a2' = fromIntegral a2} in 
  foo'_ a1' a2' >>= \res ->
  return ()

However, the current version of C2Hs (0.16.5 in my case) ignores the Haddocks.

[EJahren]

One cannot comment Enum fields either, however,
this could be fixed with #70 by writing the data
declaration by hand in addition to the enum hook.

This issue could be fixed in a similar manner if one
could tell the fun hook to not produce a type
declaration.