Rearranged all modules to enhance understanding of their purpose

and relative order (and maybe even reduce some overhead), but without
changing their effective (per-hook) calling order.  Added a
bunch of comments and removed some stray TABs.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@78040 13f79535-47bb-0310-9956-ffa450edef68