Stage #1 of the aaa rewrite - refactoring modules.

All modules are reorganized under the following scheme:
- mod_auth_*:   Front-end (basic, digest)
- mod_authn_*:  Authentication (anon, dbm, default, file)
- mod_authz_*:  Authorization (dbm, default, groupfile, host, user)

This passes the httpd-test suite when it accounts for the renaming of
aaa modules.

Originally written by: Dirk-Willem van Gulik
Completed by: Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@96728 13f79535-47bb-0310-9956-ffa450edef68