[GHC] #3384: Add HsSyn prettyprinter tests

[GHC]

#3384: Add HsSyn prettyprinter tests
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        Reporter:  igloo             |            Owner:
            Type:  task              |           Status:  new
        Priority:  normal            |        Milestone:  _|_
       Component:  Test Suite        |          Version:  6.10.4
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Changes (by kseo):

 * failure:   => None/Unknown


Comment:

 I'd like to work on this task as my first patch to GHC. I think the idea
 suggested by dfranke in #1966 is a good starting point.

 Take some large Haskell projects and:

 1. Parse them
 1. Pretty-print them
 1. Reparse the output
 1. Pretty-print again

 and verify that step 3 succeeds and the outputs of steps 2 and 4 match.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3384#comment:1>
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