update unicode FilePath handling

Based on http://hackage.haskell.org/trac/ghc/ticket/3307 ,
whether FilePath contains decoded unicode varies by OS.
So, add a configure check for it.

Also, renamed showFile to filePathToString

Backend/File.hs

@@ -193,14 +193,14 @@ checkKeyNumCopies key file numcopies = do
 
 missingNote :: String -> Int -> Int -> String -> String
 missingNote file 0 _ [] = 
-		"** No known copies of " ++ showFile file ++ " exist!"
+		"** No known copies of " ++ filePathToString file ++ " exist!"
 missingNote file 0 _ untrusted =
-		"Only these untrusted locations may have copies of " ++ showFile file ++
+		"Only these untrusted locations may have copies of " ++ filePathToString file ++
 		"\n" ++ untrusted ++
 		"Back it up to trusted locations with git-annex copy."
 missingNote file present needed [] =
 		"Only " ++ show present ++ " of " ++ show needed ++ 
-		" trustworthy copies of " ++ showFile file ++ " exist." ++
+		" trustworthy copies of " ++ filePathToString file ++ " exist." ++
 		"\nBack it up with git-annex copy."
 missingNote file present needed untrusted = 
 		missingNote file present needed [] ++

Backend/SHA1.hs

@@ -58,5 +58,5 @@ checkKeySHA1 key = do
 				then return True
 				else do
 					dest <- moveBad key
-					warning $ "Bad file content; moved to " ++ showFile dest
+					warning $ "Bad file content; moved to " ++ filePathToString dest
 					return False

Backend/WORM.hs

@@ -67,5 +67,5 @@ checkKeySize key = do
 				then return True
 				else do
 					dest <- moveBad key
-					warning $ "Bad file size; moved to " ++ showFile dest
+					warning $ "Bad file size; moved to " ++ filePathToString dest
 					return False