Document SPECIALISE for imported functions
Document SPECIALISE for imported functions

This is a really useful new facility, but I'd forgotten to document it.
Pls merge to 7.0 branch

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