Use a separate setter for shared connection manager flag

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1593927 13f79535-47bb-0310-9956-ffa450edef68
HTTPCLIENT-1508: use actual JRE version when generating default User-Agent header

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1594807 13f79535-47bb-0310-9956-ffa450edef68
Replaced dynamic proxies with custom proxy classes to reduce thread contention

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1597035 13f79535-47bb-0310-9956-ffa450edef68
Improved parameterized tests

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1603109 13f79535-47bb-0310-9956-ffa450edef68