Change html manual encoding to UTF-8.

This works around GitHub's broken automatic reformatting from ISO-8859-1
to UTF-8 when serving static html.

Remove <parameter/> from e.g. <function>malloc<parameter/></function>,
add a custom template that does not append parentheses, and manually
specify them, e.g. <function>malloc()</function>.  This works around
apparently broken XSL formatting that causes <code/> to be emitted in
html (rather than <code></code>, or better yet, nothing).