[GHC] #5942: implement POSIX confstr() in System/Posix/Unistd.hsc

[GHC]

#5942: implement POSIX confstr() in System/Posix/Unistd.hsc
-------------------------------+--------------------------------------------
  Reporter:  clint             |          Owner:                         
      Type:  feature request   |         Status:  new                    
  Priority:  normal            |      Milestone:  7.6.1                  
 Component:  libraries/unix    |        Version:  7.4.1                  
Resolution:                    |       Keywords:  confstr                
        Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple       
   Failure:  None/Unknown      |     Difficulty:  Easy (less than 1 hour)
  Testcase:                    |      Blockedby:                         
  Blocking:                    |        Related:                         
-------------------------------+--------------------------------------------

Comment(by simonmar):

 In general it's not OK to have platform-conditional APIs in the `unix`
 package.  Typically a missing function will throw an exception (e.g.
 `getSlaveTerminalName`), or fall back to a portable version (e.g.
 `unsetEnv`).  Where there are constants or symbols that need to be
 conditional, we use a `.Exts` module (see e.g.
 `System.Posix.Signals.Exts`).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5942#comment:6>
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