git: Bring in OpenBSD's mandoc(1) tool for formatting manual pages.

[justin at shiningsilence.com]

>
> commit 589e7c1db2b008d569817318dd8d8a990d926686
> Author: Sascha Wildner <saw at online.de>
> Date:   Tue Oct 27 09:42:29 2009 +0100
>
>     Bring in OpenBSD's mandoc(1) tool for formatting manual pages.
>
>     It's not (yet) used by anything but it is quite useful for
>     error checking.
>
>     Thanks to Kristaps Dzonsons and OpenBSD!

Oooh, I really like the HTML pages this tool generates.  There's probably
a way we can autogenerate them like we do for the current man page search,
and add them to www.dragonflybsd.org - Our man pages are pretty thorough,
and I'd like them to turn up in document searches with everything else.