PR 43211: Revise mod_authn_dbd documenation to reflect current APR DBD

query statement parameter requirements.  Tidy up examples and links to
glossary and external sites.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@641535 13f79535-47bb-0310-9956-ffa450edef68