formal changes:

- <em> -> <var>
- markup improvements
- allow class attribute for <li>

content changes:
- remove the references to apache 1.3 in IndexOptions descriptions
- clarify (prior non-existing) incremental index options example...


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97412 13f79535-47bb-0310-9956-ffa450edef68