Summary:
The spiritual successor to D2291, since deriving `Bounded` instances
in `GHC.Enum` wasn't possible prior to changes made in that Diff.

This Diff finds every manually implemented `Bounded` instance in `base` that is
completely equivalent to the derived instances, and replaces it.

Reviewers: bgamari, goldfire, austin, hvr

Reviewed By: austin, hvr

Subscribers: thomie, rwbarton

Differential Revision: https://phabricator.haskell.org/D2301