[GHC] #9870: Document deviation of Data.List.splitAt from Report semantics

[GHC]

#9870: Document deviation of Data.List.splitAt from Report semantics
-------------------------------------+-------------------------------------
       Reporter:  dfeuer             |                   Owner:
           Type:  task               |                  Status:  new
       Priority:  normal             |               Milestone:  7.10.1
      Component:  Documentation      |                 Version:  7.9
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Easy (less than 1  |         Type of failure:
  hour)                              |  Documentation bug
     Blocked By:                     |               Test Case:
Related Tickets:                     |                Blocking:
                                     |  Differential Revisions:  Phab:D562
-------------------------------------+-------------------------------------
 `Data.List.splitAt` is strict in its first argument. The Report specifies
 that `splitAt n xs = (take n xs, drop n xs)`. This should be noted in the
 user's guide.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9870>
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