Cabal revisions of free-5.1

Hackage metadata revisions edit the .cabal file after upload; each diff below is one revision.

 name:          free category:      Control, Monads version:       5.1+x-revision: 1 license:       BSD3 cabal-version: 1.18 license-file:  LICENSE     GADTs    build-depends:-    base                 == 4.*,+    base                 == 4.* && <4.13,     comonad              >= 4 && < 6,     distributive         >= 0.2.1,     mtl                  >= 2.0.1.0 && < 2.3,