Another DBCP 2 update.
This is the last functional update expected before the DBCP 2.0 release. There may be a few more interim updates as things are cleaned up in preparation for the DBCP 2.0 release.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1571699 13f79535-47bb-0310-9956-ffa450edef68