Messages of the -Wbase level now print STYLE:. Since this
causes horrible churn anyway, profit of the opportunity to stop
excessive testing, such that this is hopefully the last instance
of such churn. Consistently use OpenBSD RCS tags, blank .Os,
blank fourth .TH argument, and Mdocdate like everywhere else.
Use -Ios=OpenBSD for platform-independent predictable output.

style message about missing blank before trailing delimiter;
inspired by mdoclint(1), and jmc@ considers it useful

Improve and test the messages about empty macros,
in particular reporting the macro names involved.