Serialize vParallelTyCons in a stable order
Serialize vParallelTyCons in a stable order

nameSetElems can introduce nondeterminism and while I haven't
observed this being a problem in practice (possibly because this
is dead code) there's no downside to doing this.

Test Plan: ./validate

Reviewers: bgamari, austin, simonpj, simonmar

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2296

GHC Trac Issues: #4012

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