[GHC] #8894: Clean up `Coercible` plumbing

[GHC]

#8894: Clean up `Coercible` plumbing
-------------------------------------+------------------------------------
        Reporter:  nomeata           |            Owner:  nomeata
            Type:  task              |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.9
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:  #8904
-------------------------------------+------------------------------------
Changes (by nomeata):

 * owner:   => nomeata


--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8894#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler