Re-implementation of the HTTPASYNC-40 fix involving an exteremely ugly work-around, a better solution requires API changes

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1553382 13f79535-47bb-0310-9956-ffa450edef68
Upgraded HttpCore to version 4.3.1

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1553383 13f79535-47bb-0310-9956-ffa450edef68
HTTPASYNC-62: code improvement
Contributed by Dmitry Potapov <potapov.d at gmail.com>

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1553385 13f79535-47bb-0310-9956-ffa450edef68