ghc-free-4.12.4-2.3

- Update to version 4.12.4 revision 0 with cabal2obs.

- update to 4.12.4
  * Add instances for ExceptT: like ErrorT, but without an Error constraint.
  * Support containers
  * Support transformers 0.5
  * Removed a number of spurious class constraints.
  * Support comonad 5

- update to 4.12.1
  * Add instances of MonadCatch and MonadThrow from exceptions to FT, FreeT and IterT.
  * semigroupoids 5, profunctors 5, and bifunctors 5 support.

- initial commit