SongUpdate: use the Storage interface, support remote files

This commit finally allows the database update to scan remote files,
e.g. using the smbclient storage plugin.  However, it is not yet
possible to configure that, therefore the feature is not accessible
yet.

src/db/update/Archive.cxx

@@ -65,7 +65,7 @@ UpdateWalk::UpdateArchiveTree(Directory &directory, const char *name)
 		Song *song = directory.FindSong(name);
 		db_unlock();
 		if (song == nullptr) {
-			song = Song::LoadFile(name, directory);
+			song = Song::LoadFile(storage, name, directory);
 			if (song != nullptr) {
 				db_lock();
 				directory.AddSong(song);