Clarify bits about role inference in users' guide.
Clarify bits about role inference in users' guide.

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