Preserve type variable names during type inference
Preserve type variable names during type inference

During unification we attempt to preserve the print-names of type variables,
so that type error messages tend to mention type variables using the 
programmer's vocabulary.  

This had bit-rotted a bit when I added impredicative polymorphism; especially
when unBoxing a boxy type variable we should not gratuitously lose its name.


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