Fixed wording, made compat explicit.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/pool/trunk@1553033 13f79535-47bb-0310-9956-ffa450edef68
Updated for 2.1 release.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/pool/trunk@1553036 13f79535-47bb-0310-9956-ffa450edef68