Prefer mdoc to man plain roff.
Use \*[Lt] and \*[Gt] instead of < and > for HTML output, but prefer
.Aq if possible.
"a, b, and c" instead of "a, b and c".
if there are any mistakes, please report (i only speak English/Japanese).
currently, only singlebyte locales are usable.
TODO: enable multibyte handler in libc - there still are few design
discussions, but we are almost ready.