Adds a clarification to the AddDescription docs, to address the

confusion indicated in https://issues.apache.org/bugzilla/show_bug.cgi?id=17210
The problem described there is fixed by a reordering of the
AddDescription directives.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@894306 13f79535-47bb-0310-9956-ffa450edef68