Export "readEither" and add "readMaybe".
Export "readEither" and add "readMaybe".

This commit implements the change discussed in the following
thread on the Haskell libraries list:

http://www.haskell.org/pipermail/libraries/2011-December/thread.html#17290

NOTE:  This only implements the change for GHC, but the change
makes sense for Hugs too... Perhaps we should simply re-implement 'readEither'
in terms of 'reads'?

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