First crack at the automatic directive index. Now the only thing that

First crack at the automatic directive index.  Now the only thing that
needs to be done if a new module is added is to stick it in allmodules.xml.
The directives will then get included in the index.

The technique in the xsl stylesheet can surely be improved, and we can
also now do fancy stuff like having a "quick reference" which includes
syntax/etc.  But this is a good start.

I haven't committed the html output of this yet, because there are still
a few modules yet to be converted to xml.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93822 13f79535-47bb-0310-9956-ffa450edef68