Always use filesystem encoding for all file and handle reads and writes.

This is a big scary change. I have convinced myself it should be safe. I
hope!

Git/HashObject.hs

@@ -41,7 +41,6 @@ hashFile h file = CoProcess.query h send receive
  - interface does not allow batch hashing without using temp files. -}
 hashBlob :: HashObjectHandle -> String -> IO Sha
 hashBlob h s = withTmpFile "hash" $ \tmp tmph -> do
-	fileEncoding tmph
 #ifdef mingw32_HOST_OS
 	hSetNewlineMode tmph noNewlineTranslation
 #endif