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/View.hs

@@ -99,7 +99,7 @@ checkoutViewBranch view mkbranch = do
 		 - and this pollutes the view, so remove them.
 		 - (However, emptry directories used by submodules are not
 		 - removed.) -}
-		top <- liftIO . absPath =<< fromRepo Git.repoPath
+		top <- liftIO . absPath . fromRawFilePath =<< fromRepo Git.repoPath
 		(l, cleanup) <- inRepo $
 			LsFiles.notInRepoIncludingEmptyDirectories False
 				[toRawFilePath top]
@@ -110,8 +110,8 @@ checkoutViewBranch view mkbranch = do
 	return ok
   where
 	removeemptydir top d = do
-		p <- inRepo $ toTopFilePath $ fromRawFilePath d
-		liftIO $ tryIO $ removeDirectory (top </> getTopFilePath p)
+		p <- inRepo $ toTopFilePath d
+		liftIO $ tryIO $ removeDirectory (top </> fromRawFilePath (getTopFilePath p))
 	cwdmissing top = unlines
 		[ "This view does not include the subdirectory you are currently in."
 		, "Perhaps you should:  cd " ++ top