Fixed remaining warning in coreSyn/MkExternalCore
Fixed remaining warning in coreSyn/MkExternalCore

There was a (suppressed) warning about an incomplete pattern match in make_alt. This was because the DEFAULT alt never has variable bindings. I thought it would be better to check that case and panic if it happens than to have an incomplete pattern. It's still not great, but at least now we don't have to suppress any warnings in this file.

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