[GHC] #9623: Use Data.List.dropWhileEnd

[GHC]

#9623: Use Data.List.dropWhileEnd
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              Reporter:  dfeuer      |            Owner:
                  Type:  task        |           Status:  patch
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Easy (less than 1
       Type of failure:              |  hour)
  None/Unknown                       |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Changes (by dfeuer):

 * status:  new => patch


Comment:

 One use of `reverse . dropWhile isSpace . reverse` turned out to be
 embedded in what someone suggested correctly was a complete
 reimplementation of `unwords . words`, so I just used that.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9623#comment:1>
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