A section 3 man page should be written to describe libxapian (see the libxml
manpage for example.)

We could also produce debug variant of the libxapian package, built with
--enable-assertions and/or --enable-log.

xapian-doc: in index.html, there is one broken link (which occurs in two
places, pointing to the "internal classes" documentation, since we don't
generate this by default).  We could move this to point to the Xapian website.
There should almost certainly be a link back to the front page of the Xapian
website, too.  The documentation should also probably be in the style of the
Xapian website, and should use the Xapian logo on the front page.
