Expand the scope of the event_buf_mutex to cover io_manager_event I once saw a failure that I think was due to a race on io_manager_event, this should fix it.
Expand the scope of the event_buf_mutex to cover io_manager_event
I once saw a failure that I think was due to a race on
io_manager_event, this should fix it.

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