Adding a newtype EndoCategory to Control.Category (ticket #3362)

[Isaac Dupree]

Edward Kmett wrote:
> Yeah, it would probably have to have a new name because it does have a
> different kind than the existing Endo. GEndo was the best I could come up
> with that didn't sound verbose (GeneralizedEndo, CategoricalEndo) or like it
> was naming the wrong thing (EndoCategory). I'm not wedded to the name by any
> means.

CatEndo?