Clean up block allocator, fixes #8609
Clean up block allocator, fixes #8609

Signed-off-by: Edward Z. Yang <dbd597f5635f432486c5d365e9bb585b3eaa1853@cs.stanford.edu>

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