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.

more tests for excessively long text in TERMP_NOBREAK mode

Implement .Fo/.Fa/.Fc indentation and break handling for -Tman.

Do not break output lines in .Fn function arguments in SYNOPSIS mode.
Following an idea from Franco Fichtner, but implemented more cleanly.
This reduces groff-mandoc-differences in base by a fantastic 7.5%.