ghc-prim: Use population count appropriate for platform
ghc-prim: Use population count appropriate for platform

Summary:
This #ifdef was previously x86-centric and consequently the 64-bit
implementation was chosen for ARM.

Reviewers: rwbarton, hvr, austin, tibbe

Reviewed By: hvr, austin, tibbe

Subscribers: hvr, thomie, carter, ezyang, simonmar

Differential Revision: https://phabricator.haskell.org/D312

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