convert TopFilePath to use RawFilePath

Adds a dependency on filepath-bytestring, an as yet unreleased fork of
filepath that operates on RawFilePath.

Git.Repo also changed to use RawFilePath for the path to the repo.

This does eliminate some RawFilePath -> FilePath -> RawFilePath
conversions. And filepath-bytestring's </> is probably faster.
But I don't expect a major performance improvement from this.
This is mostly groundwork for making Annex.Location use RawFilePath,
which will allow for a conversion-free pipleline.

Database/ContentIdentifier.hs

@@ -145,7 +145,7 @@ updateFromLog db (oldtree, currtree) = do
 		recordAnnexBranchTree db currtree
 		flushDbQueue db
   where
-	go ti = case extLogFileKey remoteContentIdentifierExt (toRawFilePath (getTopFilePath (DiffTree.file ti))) of
+	go ti = case extLogFileKey remoteContentIdentifierExt (getTopFilePath (DiffTree.file ti)) of
 		Nothing -> return ()
 		Just k -> do
 			l <- Log.getContentIdentifiers k