Update documentation of intersectBy
Update documentation of intersectBy

Mention which list is the source
of the elements in the resulting list.

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