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.

In markdown, autolinks are dangerous. Different compilers disagree
with respect to what constitutes a valid autolink, and if a compiler
deems an autolink invalid, the input turns into an unintended and
potentially harmful raw HTML tag. So, never write autolinks.
Instead of <link>, write [link](link).
Instead of <addr>, write [addr](mailto:addr).

Issue pointed out by bentley@, who also agrees with the general
direction of the change.

URIs need different escaping; reported by reyk@

first batch of -T markdown tests