Enhance documentation of --add-module and --activate-module

Submitted by: David Harris <dharris@drh.net>
Reviewed by: Ralf S. Engelschall


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@83843 13f79535-47bb-0310-9956-ffa450edef68