when calling aug_match() escape special characters in components of paths
    
    As with aug_get(), most of the calls to aug_match() either use paths
    that are themselves returned from aug_match() (in which case they are
    already escaped), they don't include any unsanitized data outside of
    single quotes, or (in one case - aug_fmt_match()) we don't know the
    nature of the data, as it is composed of asprintf arguments; in this
    final case, we will do a separate patch looking at eash of the callers
    to aug_fmt_match().