Recent changes in categories breaks algebra

[jmcarthur]

In particular, algebra uses the Control.Categorical.* namespace.

[ekmett]

I'm slowly working my way through what categories should be when it grows up.

Not sure I want to push out the version there in categories HEAD as it would make algebra 7.8 specific, and worse it'd break pipes.

I'd be open to rolling back slightly and making a Control.Categorical.Category that just re-exports Control.Category on modern GHCs. I should probably cherry pick the 7.8 fixes back into something closer to the current released version to maintain maximum flexibility for users, with the few hierarchy around Associated/Monoidal going in as part of that release.