Log reason when mod_dir returns access HTTP_FORBIDDEN

Reviewed by: Rob Hartill, Randy Terbush
Submitted by: Ken the Rodent of Unusual Size


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@77434 13f79535-47bb-0310-9956-ffa450edef68