Support 'mdo'.
Tibbe-style 'where' indentation.
Highlighting tweaks.
Copy vim2hs' conceal syntax rules.
Comments.
Remove '_' as a keyword.
Highlight type variables.
More type syntax work.
Misc.
Distinguish type and data constructors.
More work in type/data highlighting.
forall.
Pipes are reserved.
Work on 'deriving'.
More data decl work.
wip