more RawFilePath

Remove dup definitions and just use the RawFilePath one. </> etc are
enough faster that it's probably faster than building a String directly,
although I have not benchmarked.

Command/AddUnused.hs

@@ -31,7 +31,7 @@ perform key = next $ do
 	addLink file key Nothing
 	return True
   where
-	file = "unused." ++ keyFile key
+	file = "unused." ++ fromRawFilePath (keyFile key)
 
 {- The content is not in the annex, but in another directory, and
  - it seems better to error out, rather than moving bad/tmp content into