hub.darcs.net :: ross -> transformers -> issue

Ryan Scott

These should absolutely, definitively, be the last changes we should have to make to transformers to make it work with GHC 8.0... I think :)

1. hvr has decreed ( https://phabricator.haskell.org/D1147#39721 ) that the version of base to be shipped with GHC 8.0 will have version 4.9.0.0, so reflect that in the CPP pragmas.
2. GHC 8.0 introduces a Monoid a => Monoid (Identity a) instance ( http://git.haskell.org/ghc.git/blobdiff/eca9a1a17c12d01636417fb88bda5ee5fe34577f..97843d0b10cac3912a85329ebcb8ed1a68f71b34:/libraries/base/Data/Functor/Identity.hs ), so backport it