Upgraded HttpCore to version 4.4-beta1

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1626968 13f79535-47bb-0310-9956-ffa450edef68
ZeroCopyConsumer: preserve content encoding
Contributed by Dmitry Potapov <dpotapov at yandex-team.ru>

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1626969 13f79535-47bb-0310-9956-ffa450edef68