is not defined.
- URL_RELPREFIX must always point the top page's URL
(http://www.FreeBSD.org) in relative form, defined in Makefile.
- &url.base; can be used in doc/<langcode>/*. It will be
replaced with the real URL which points the top page.
For translators: Please make sure to define URL_RELPREFIX to
point the top page. The localized docs have different directory
hierarchy in its URL from the English version.
Tested by: den
