When parsing a metric_fu-formatted rcov.txt, lines will be identified the same as simplecov 0, 1, nil for missed, covered, ignored, respectively.

When parsing an rcov-formatted rcov.txt, lines will be identified as missed if they start with '!!' else covered which is the same as the old RCov behavior, as confirmed by one of the intermediary PR commits where the rcov-fixture actually had 0% coverage (quite correctly) per the SimpleCov rubric.