Fix bug that caused ghci to create a large number of kqueues and pipes on OS X.
Fix bug that caused ghci to create a large number of kqueues and pipes on OS X.

This is caused because ensureIOManagerIsRunning is repeatedly called and this was initializing new IO managers on each call. Fixed so that a new manager is not created if one already exists.

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