Change DocBook XSL parameters for HTML output to use numbered sections
(like it was before we switched from SGML to XML) and to use just the
numbers in cross references, rather than number and/or title.
This makes sure the HTML output for
<function>foo<parameter>bar</parameter><parameter>baz</parameter></function>
includes parentheses, although it doesn't seem to add empty parentheses
after a plain <function>foo</function> which perhaps it should.
