Fix apparently-long-standing bug in FloatIn
Fix apparently-long-standing bug in FloatIn

The float-in pass wasn't doing the right thing when you have

	let x{rule mentions y} = rhs in body

It allowed a binding mentioning y to float into the body, which is
obviously wrong.  I think this bug has been there a long time; I don't
really know why it has not come up before.

It showed up when compiling Text.Regex.Base.Context with WAY=p in
package regex-base.


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