[GHC] #12464: Add `instance Semigroup a => Semigroup (IO a)`

[GHC]

#12464: Add `instance Semigroup a => Semigroup (IO a)`
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           Reporter:  Iceland_jack   |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Core           |           Version:  8.0.1
  Libraries                          |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 What the title says

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12464>
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