PostTcType replaced with TypeAnnot
PostTcType replaced with TypeAnnot

Summary: Compiles and passes validate. Transition in renamer

Test Plan: sh validate

Reviewers: austin

Subscribers: simonmar, relrod, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D157

holzensp/ghc,holzensp/ghc,holzensp/ghc,holzensp/ghc,holzensp/ghc