Figure out how to create various instances on arbitrary fixed-point types.

[sellout]

E.g., is there something we can do, like (Recursive t f, PatternMonoid f) => Monoid t (where PatternMonoid is the missing piece), and similarly for other type classes.

We have (or maybe used to have?) things like this for Functor and Foldable, but should try to expand it as much as possible. I think I remember seeing some instances like this in the Haskell world (perhaps in @pa-ba /compdata).