[GHC] #974: Add isLeft, isRight, fromLeft, fromRight, and splitEithers to Data.Either

[GHC]

#974: Add isLeft, isRight, fromLeft, fromRight, and splitEithers to Data.Either
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    Reporter:  guest           |       Owner:         
        Type:  proposal        |      Status:  new    
    Priority:  normal          |   Milestone:         
   Component:  libraries/base  |     Version:  6.6    
    Severity:  normal          |    Keywords:         
  Difficulty:  Unknown         |    Testcase:         
Architecture:  Unknown         |          Os:  Unknown
-------------------------------+--------------------------------------------
This proposal would add basic functionality to `Either` similar to that
 for `Maybe`.  The `splitEithers` function of type `[Either a b] ->
 ([a],[b])` is unique; however, it seems to be a widely useful function.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/974>
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