run-tests: add flag to provide extra hgrc options for test runs

graphlog: always sort revisions topologically The grapher cannot really handled revisions if they are not emitted in topological order. The previous 'reverse()' revset was not enough to achieve that and was replaced by an explicit sort call for simplicity. The --limit option is now also handled as usual with cmdutil.loglimit() instead of a 'limit' revset.