Avoid repeatedly loading GHC.Prim
Avoid repeatedly loading GHC.Prim

This patch changes HscTypes.lookupIfaceByModule.  The problem was that
when compiling the 'base' package, we'd repeatedly reload GHC.Prim.
This is easily fixed by looking in the PIT too. A comment with
lookupIfaceByModule explains


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