[GHC] #10755: Add `MonadPlus IO` and `Alternative IO` instances

[GHC]

#10755: Add `MonadPlus IO` and `Alternative IO` instances
-------------------------------------+-------------------------------------
              Reporter:  hvr         |             Owner:
                  Type:  task        |            Status:  new
              Priority:  normal      |         Milestone:  7.12.1
             Component:  Core        |           Version:
  Libraries                          |
              Keywords:  report-     |  Operating System:  Unknown/Multiple
  impact                             |
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
-------------------------------------+-------------------------------------
 Cloned and adapted from #9588:
 ----
 The following 2 instances are currently Orphans in `transformers` but
 shall be defined in `base` instead:

 {{{#!hs
 instance MonadPlus IO
 instance Alternative IO
 }}}

 This proposal by SPJ already passed the CLC back in April and only needs
 implementing. I'll submit a patch shortly to Phab

 ----

 This needs coordination w/ Ross as `transformers` must not define the same
 instances for new enough `base` versions.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10755>
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