Add a warning to the docs for future developers.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1622004 13f79535-47bb-0310-9956-ffa450edef68
Changelog for the RFC6265 cookie parser

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1622008 13f79535-47bb-0310-9956-ffa450edef68