Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=12428
Add optional support for preemptive authentication on a per context basis
Based on a patch suggested by Werner Donn
This includes the fix for CVE-2011-1183
git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1087643 13f79535-47bb-0310-9956-ffa450edef68