TcRnMonad: make forkM thread-safe
TcRnMonad: make forkM thread-safe

A forkM'd action cannot safely share a UniqSupply with its parent.

[ Originally I resolved this issue in another way: by atomically
  updating env_us in newUnique/newUniqueSupply. But I think this
  (equivalent) change is more sensible. ]

spacekitteh/smcghc,mcschroeder/ghc,ryantm/ghc,wxwxwwxxx/ghc,vTurbine/ghc,wxwxwwxxx/ghc,hferreiro/replay,hferreiro/replay,nathyong/microghc-ghc,ezyang/ghc,ml9951/ghc,wxwxwwxxx/ghc,elieux/ghc,da-x/ghc,gcampax/ghc,mfine/ghc,AlexanderPankiv/ghc,nathyong/microghc-ghc,nkaretnikov/ghc,forked-upstream-packages-for-ghcjs/ghc,lukexi/ghc,bitemyapp/ghc,oldmanmike/ghc,sgillespie/ghc,hferreiro/replay,forked-upstream-packages-for-ghcjs/ghc,TomMD/ghc,anton-dessiatov/ghc,ezyang/ghc,ghc-android/ghc,TomMD/ghc,snoyberg/ghc,gcampax/ghc,mfine/ghc,tjakway/ghcjvm,TomMD/ghc,urbanslug/ghc,lukexi/ghc,gridaphobe/ghc,spacekitteh/smcghc,nkaretnikov/ghc,ekmett/ghc,vikraman/ghc,da-x/ghc,shlevy/ghc,vTurbine/ghc,elieux/ghc,elieux/ghc,oldmanmike/ghc,ekmett/ghc,shlevy/ghc,vikraman/ghc,siddhanathan/ghc,vTurbine/ghc,urbanslug/ghc,christiaanb/ghc,christiaanb/ghc,green-haskell/ghc,sdiehl/ghc,tjakway/ghcjvm,ghc-android/ghc,shlevy/ghc,forked-upstream-packages-for-ghcjs/ghc,oldmanmike/ghc,tibbe/ghc,nushio3/ghc,ezyang/ghc,mettekou/ghc,frantisekfarka/ghc-dsi,nkaretnikov/ghc,ghc-android/ghc,olsner/ghc,jstolarek/ghc,fmthoma/ghc,fmthoma/ghc,vikraman/ghc,TomMD/ghc,ghc-android/ghc,fmthoma/ghc,mettekou/ghc,mettekou/ghc,sgillespie/ghc,sdiehl/ghc,green-haskell/ghc,nathyong/microghc-ghc,da-x/ghc,lukexi/ghc-7.8-arm64,vikraman/ghc,TomMD/ghc,acowley/ghc,ml9951/ghc,bitemyapp/ghc,acowley/ghc,oldmanmike/ghc,da-x/ghc,mcschroeder/ghc,ml9951/ghc,gridaphobe/ghc,mcschroeder/ghc,spacekitteh/smcghc,shlevy/ghc,fmthoma/ghc,christiaanb/ghc,ryantm/ghc,nathyong/microghc-ghc,AlexanderPankiv/ghc,nkaretnikov/ghc,ezyang/ghc,mcschroeder/ghc,tibbe/ghc,elieux/ghc,mfine/ghc,lukexi/ghc,ml9951/ghc,AlexanderPankiv/ghc,anton-dessiatov/ghc,gcampax/ghc,olsner/ghc,elieux/ghc,mfine/ghc,tjakway/ghcjvm,vikraman/ghc,nkaretnikov/ghc,frantisekfarka/ghc-dsi,wxwxwwxxx/ghc,jstolarek/ghc,urbanslug/ghc,AlexanderPankiv/ghc,ezyang/ghc,mcschroeder/ghc,ezyang/ghc,gcampax/ghc,wxwxwwxxx/ghc,shlevy/ghc,jstolarek/ghc,acowley/ghc,siddhanathan/ghc,GaloisInc/halvm-ghc,gridaphobe/ghc,mfine/ghc,snoyberg/ghc,acowley/ghc,snoyberg/ghc,lukexi/ghc-7.8-arm64,ekmett/ghc,ekmett/ghc,gridaphobe/ghc,nkaretnikov/ghc,siddhanathan/ghc,mettekou/ghc,forked-upstream-packages-for-ghcjs/ghc,snoyberg/ghc,GaloisInc/halvm-ghc,vTurbine/ghc,olsner/ghc,nushio3/ghc,GaloisInc/halvm-ghc,bitemyapp/ghc,anton-dessiatov/ghc,TomMD/ghc,hferreiro/replay,elieux/ghc,da-x/ghc,tjakway/ghcjvm,snoyberg/ghc,snoyberg/ghc,acowley/ghc,gridaphobe/ghc,bitemyapp/ghc,urbanslug/ghc,siddhanathan/ghc,vTurbine/ghc,shlevy/ghc,urbanslug/ghc,snoyberg/ghc,holzensp/ghc,vTurbine/ghc,acowley/ghc,mettekou/ghc,ghc-android/ghc,gridaphobe/ghc,vikraman/ghc,olsner/ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,da-x/ghc,ghc-android/ghc,frantisekfarka/ghc-dsi,olsner/ghc,acowley/ghc,anton-dessiatov/ghc,gcampax/ghc,lukexi/ghc,wxwxwwxxx/ghc,hferreiro/replay,sgillespie/ghc,forked-upstream-packages-for-ghcjs/ghc,spacekitteh/smcghc,fmthoma/ghc,ml9951/ghc,forked-upstream-packages-for-ghcjs/ghc,tjakway/ghcjvm,sgillespie/ghc,ml9951/ghc,green-haskell/ghc,sdiehl/ghc,ghc-android/ghc,mettekou/ghc,holzensp/ghc,siddhanathan/ghc,AlexanderPankiv/ghc,sdiehl/ghc,forked-upstream-packages-for-ghcjs/ghc,mfine/ghc,green-haskell/ghc,lukexi/ghc-7.8-arm64,anton-dessiatov/ghc,tibbe/ghc,vikraman/ghc,urbanslug/ghc,sdiehl/ghc,nathyong/microghc-ghc,tibbe/ghc,frantisekfarka/ghc-dsi,nushio3/ghc,jstolarek/ghc,urbanslug/ghc,lukexi/ghc-7.8-arm64,nushio3/ghc,da-x/ghc,oldmanmike/ghc,nushio3/ghc,sgillespie/ghc,lukexi/ghc-7.8-arm64,christiaanb/ghc,mfine/ghc,GaloisInc/halvm-ghc,ml9951/ghc,sdiehl/ghc,gcampax/ghc,tjakway/ghcjvm,shlevy/ghc,fmthoma/ghc,bitemyapp/ghc,nushio3/ghc,christiaanb/ghc,jstolarek/ghc,mcschroeder/ghc,ryantm/ghc,hferreiro/replay,elieux/ghc,gcampax/ghc,ekmett/ghc,spacekitteh/smcghc,holzensp/ghc,frantisekfarka/ghc-dsi,holzensp/ghc,christiaanb/ghc,sgillespie/ghc,GaloisInc/halvm-ghc,TomMD/ghc,oldmanmike/ghc,tjakway/ghcjvm,wxwxwwxxx/ghc,nathyong/microghc-ghc,nathyong/microghc-ghc,ryantm/ghc,christiaanb/ghc,hferreiro/replay,ezyang/ghc,nkaretnikov/ghc,ml9951/ghc,oldmanmike/ghc,fmthoma/ghc,AlexanderPankiv/ghc,olsner/ghc,holzensp/ghc,gridaphobe/ghc,vTurbine/ghc,nushio3/ghc,siddhanathan/ghc,mcschroeder/ghc,anton-dessiatov/ghc,ryantm/ghc,siddhanathan/ghc,mettekou/ghc,sdiehl/ghc,tibbe/ghc,olsner/ghc,sgillespie/ghc,green-haskell/ghc,lukexi/ghc,AlexanderPankiv/ghc,anton-dessiatov/ghc