[GHC] #673: Import FastPackedStrings for 6.6

[GHC]

#673: Import FastPackedStrings for 6.6
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    Reporter:  simonmar        |        Owner:                  
        Type:  task            |       Status:  new             
    Priority:  normal          |    Milestone:  6.6             
   Component:  libraries/base  |      Version:  6.4.1           
    Severity:  normal          |     Keywords:                  
          Os:  Unknown         |   Difficulty:  Moderate (1 day)
Architecture:  Unknown         |  
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6.6 must have a better PackedString library, probably based on ForeignPtr
 (probably a combination of [http://www.cse.unsw.edu.au/~dons/fps.html
 FastPackedStrings] and simonmar's version).  I'm not sure how we go about
 deprecating the current interface and adding the new one yet.

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Ticket URL: <http://cvs.haskell.org/trac/ghc/ticket/673>
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