Add some documentation to IOEnv.
Add some documentation to IOEnv.

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