[GHC] #1880: Unify flag descriptions to generate both docs and code

[GHC]

#1880: Unify flag descriptions to generate both docs and code
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    Reporter:  simonmar  |       Owner:             
        Type:  task      |      Status:  new        
    Priority:  normal    |   Milestone:  6.10 branch
   Component:  Compiler  |     Version:  6.8.1      
    Severity:  normal    |    Keywords:             
  Difficulty:  Unknown   |    Testcase:             
Architecture:  Unknown   |          Os:  Unknown    
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 We want to specify all of GHC's flags in one place, and from there

  * Generate the flag reference section of the documentation
  * Generate the code to parse the command-line
  * Allow flags to be deprecated, generating a warning
  * Have an option to list all the flags that GHC supports (see #1226)
    for use in command-line completion
  * Generate the man page

 This ticket replaces part of #1226.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1880>
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