Do not automatically close HttpAsyncRequestExecutionHandler on an I/O error allowing the handler to retry

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1439907 13f79535-47bb-0310-9956-ffa450edef68
Redesign of the client exchange handler API

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1439908 13f79535-47bb-0310-9956-ffa450edef68
HTTPASYNC-34: a proper fix for incorrect handling of prematurely termination of a persistent connection by the opposite end

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1439909 13f79535-47bb-0310-9956-ffa450edef68