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.

Command/Log.hs

@@ -199,7 +199,7 @@ compareChanges format changes = concatMap diff changes
 getKeyLog :: Key -> [CommandParam] -> Annex ([RefChange], IO Bool)
 getKeyLog key os = do
 	top <- fromRepo Git.repoPath
-	p <- liftIO $ relPathCwdToFile top
+	p <- liftIO $ relPathCwdToFile $ fromRawFilePath top
 	config <- Annex.getGitConfig
 	let logfile = p </> fromRawFilePath (locationLogFile config key)
 	getGitLog [logfile] (Param "--remove-empty" : os)