backport from trunk and 2.2.x:

   SECURITY: CAN-2005-2700 (cve.mitre.org)
   mod_ssl: Fix a security issue where "SSLVerifyClient" was not
   enforced in per-location context if "SSLVerifyClient optional"
   was configured in the vhost configuration.

Submitted by: Joe Orton
Reviewed by: wrowe, trawick
  


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@307220 13f79535-47bb-0310-9956-ffa450edef68