Make Unique a newtype
Make Unique a newtype

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2432

olsner/ghc,sdiehl/ghc,olsner/ghc,ezyang/ghc,sdiehl/ghc,sgillespie/ghc,shlevy/ghc,olsner/ghc,sgillespie/ghc,ezyang/ghc,snoyberg/ghc,snoyberg/ghc,sdiehl/ghc,sdiehl/ghc,sgillespie/ghc,mettekou/ghc,sgillespie/ghc,olsner/ghc,snoyberg/ghc,snoyberg/ghc,shlevy/ghc,olsner/ghc,sdiehl/ghc,sgillespie/ghc,shlevy/ghc,mettekou/ghc,shlevy/ghc,ezyang/ghc,olsner/ghc,sgillespie/ghc,mettekou/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,mettekou/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,olsner/ghc,ezyang/ghc,mettekou/ghc,mettekou/ghc,sdiehl/ghc,snoyberg/ghc,snoyberg/ghc,mettekou/ghc,sgillespie/ghc,shlevy/ghc,snoyberg/ghc