so update the example to use the correct definition.
Add an example for documenting kernel compile options, along with
a small example of how to reference them in the main text of the
man page (I.e. the .Dv macro).
Inspired-by: a brief exchange I saw in in the commit messages mail
Add all of the possible errno's to example.3.
Show examples of the .Bx (BSD) and .At (AT&T UNIX) macros
in the various HISTORY sections.
Add some .Rs/.Re (used for referencing things other
than man pages) in the SEE ALSO sections.
Suggested by: wollman
since it seemed like a better place, and the makefiles for
/usr/share/examples didn't need to be fussed with.
The old stuff can be removed from the Attic.
