cause a lookup failure of external rewrite maps, if the key contains a \n

PR: 14453
Reviewed by: Jeff Trawick, Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@102278 13f79535-47bb-0310-9956-ffa450edef68