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.

Logs/Web.hs

@@ -93,7 +93,7 @@ knownUrls = do
 	Annex.Branch.update
 	Annex.Branch.commit =<< Annex.Branch.commitMessage
 	Annex.Branch.withIndex $ do
-		top <- toRawFilePath <$> fromRepo Git.repoPath
+		top <- fromRepo Git.repoPath
 		(l, cleanup) <- inRepo $ Git.LsFiles.stagedDetails [top]
 		r <- mapM getkeyurls l
 		void $ liftIO cleanup