[GHC] #7758: Remove cg_tag field from CgIdInfo

[GHC]

#7758: Remove cg_tag field from CgIdInfo
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Reporter:  bosu              |          Owner:                  
    Type:  task              |         Status:  new             
Priority:  normal            |      Component:  Compiler        
 Version:  7.7               |       Keywords:                  
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
 Failure:  None/Unknown      |      Blockedby:                  
Blocking:                    |        Related:                  
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 Apparently it is used nowhere now.

 To do the removal I've needed to detabify StgCmmEnv.hs, StgCmmMonad.hs
 first.

 Respective patches are attached.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7758>
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