[GHC] #5420: writeFile should use openBinaryFile

[GHC]

#5420: writeFile should use openBinaryFile
---------------------------------+------------------------------------------
    Reporter:  Tinctorius        |       Owner:              
        Type:  bug               |      Status:  new         
    Priority:  normal            |   Component:  Compiler    
     Version:  7.2.1             |    Keywords:              
    Testcase:                    |   Blockedby:              
          Os:  Unknown/Multiple  |    Blocking:              
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown
---------------------------------+------------------------------------------
 Apparently, I can't use `writeFile` to write binary data to a file in
 Windows:

 {{{
 Prelude Codec.Binary.Base64.String Data.Char> readFile "foo.txt"
   >>= return . decode . filter isAlphaNum >>= writeFile "foo.dat"
 *** Exception: .../foo.dat: commitBuffer: invalid argument
   (character is not in the code page)
 }}}

 This is clearly because `openFile` opens the file with newline translation
 etc. (why would you ever want this by default? D:). `writeFile` does not
 mention this behaviour in its documentation.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5420>
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