HTTPCORE-341: Added methods to enumerate all available and leased connections in connection pool

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1489746 13f79535-47bb-0310-9956-ffa450edef68
HTTPCORE-341: Added methods to enumerate all available and leased connections in connection pool (fixed java 1.5 compatibility)

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1489753 13f79535-47bb-0310-9956-ffa450edef68