[GHC] #7902: Add support for byte endianness swapping exposed as a primops

[GHC]

#7902: Add support for byte endianness swapping exposed as a primops
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  Reporter:  tab                          |          Owner:                  
      Type:  feature request              |         Status:  new             
  Priority:  normal                       |      Milestone:                  
 Component:  Compiler                     |        Version:  7.7             
Resolution:                               |       Keywords:  bswap endianness
        Os:  Unknown/Multiple             |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown                 |     Difficulty:  Unknown         
  Testcase:  codeGen/should_run/cgrun072  |      Blockedby:                  
  Blocking:                               |        Related:                  
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Comment(by tab):

 By incremental, I mean it apply on the previously applied (but now
 reverted) patches. i can fold the patches together in one if it's better,
 but I thought it could be useful for everyone to see what I changed.

 I'm reasonably confident it's mergeable now.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7902#comment:18>
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