Improve hierarchical module name handling in MkExternalCore
Improve hierarchical module name handling in MkExternalCore

It's easier for the External Core parser if MkExternalCore prints
module names like:
   base:GHCziBase
rather than like:
   base:GHC.Base
(which it was doing before.)

So now we z-encode the hierarchical module-name part of a module
name, but don't z-encode the ':'.

I also removed some old comments that don't seem relevant anymore.

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