Update the name cache when creating new names via DeriveGeneric
Update the name cache when creating new names via DeriveGeneric

New external top-level names were being created but the name cache
wasn't being populated, leading to #7878.

Signed-off-by: Jose Pedro Magalhaes <815e8f570865f2efd141c7915958bae99974cc88@cs.ox.ac.uk>

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