unreg: handle CmmStack in C codegen (unbreaks '-g')
unreg: handle CmmStack in C codegen (unbreaks '-g')

The patch makes
    $ make test TEST="debug T10667"
not to fail on CmmStack code generation phase

Signed-off-by: Sergei Trofimovich <df7d2cee2e7ececeb2368216a0f9d0537fd32149@google.com>

mettekou/ghc,mettekou/ghc,ezyang/ghc,gridaphobe/ghc,mcschroeder/ghc,oldmanmike/ghc,da-x/ghc,olsner/ghc,vTurbine/ghc,nushio3/ghc,nushio3/ghc,oldmanmike/ghc,snoyberg/ghc,elieux/ghc,oldmanmike/ghc,nushio3/ghc,olsner/ghc,sdiehl/ghc,GaloisInc/halvm-ghc,vTurbine/ghc,mcschroeder/ghc,snoyberg/ghc,shlevy/ghc,snoyberg/ghc,olsner/ghc,shlevy/ghc,mcschroeder/ghc,sdiehl/ghc,mettekou/ghc,AlexanderPankiv/ghc,ezyang/ghc,snoyberg/ghc,oldmanmike/ghc,vikraman/ghc,sgillespie/ghc,gridaphobe/ghc,da-x/ghc,mcschroeder/ghc,da-x/ghc,GaloisInc/halvm-ghc,elieux/ghc,snoyberg/ghc,gridaphobe/ghc,snoyberg/ghc,vTurbine/ghc,nushio3/ghc,vikraman/ghc,oldmanmike/ghc,vikraman/ghc,olsner/ghc,shlevy/ghc,sgillespie/ghc,oldmanmike/ghc,ezyang/ghc,gridaphobe/ghc,AlexanderPankiv/ghc,GaloisInc/halvm-ghc,olsner/ghc,elieux/ghc,mcschroeder/ghc,tjakway/ghcjvm,shlevy/ghc,ezyang/ghc,mcschroeder/ghc,olsner/ghc,ezyang/ghc,vikraman/ghc,AlexanderPankiv/ghc,nushio3/ghc,shlevy/ghc,GaloisInc/halvm-ghc,sgillespie/ghc,sgillespie/ghc,elieux/ghc,mettekou/ghc,tjakway/ghcjvm,da-x/ghc,tjakway/ghcjvm,GaloisInc/halvm-ghc,mettekou/ghc,snoyberg/ghc,sgillespie/ghc,vikraman/ghc,shlevy/ghc,gridaphobe/ghc,da-x/ghc,mcschroeder/ghc,vikraman/ghc,oldmanmike/ghc,gridaphobe/ghc,da-x/ghc,GaloisInc/halvm-ghc,nushio3/ghc,AlexanderPankiv/ghc,vTurbine/ghc,sdiehl/ghc,ezyang/ghc,GaloisInc/halvm-ghc,tjakway/ghcjvm,tjakway/ghcjvm,sgillespie/ghc,vTurbine/ghc,tjakway/ghcjvm,sgillespie/ghc,nushio3/ghc,sdiehl/ghc,AlexanderPankiv/ghc,AlexanderPankiv/ghc,vTurbine/ghc,tjakway/ghcjvm,mettekou/ghc,elieux/ghc,sdiehl/ghc,mettekou/ghc,AlexanderPankiv/ghc,sdiehl/ghc,vTurbine/ghc,ezyang/ghc,shlevy/ghc,da-x/ghc,elieux/ghc,gridaphobe/ghc,sdiehl/ghc,elieux/ghc,olsner/ghc,vikraman/ghc