Mention that `Data.Ix` uses row-major indexing
Mention that `Data.Ix` uses row-major indexing

This addresses Trac #8712 by simply mentioning row-major indexing,
thereby removing any ambiguity.

Signed-off-by: Austin Seipp <7ea35d812706d9213868749011af1ed4fa2f6aa0@well-typed.com>

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