HTTPCLIENT-1497: Allow zero SO_LINGER (immediate abortive close)
Contributed by Dmitry Potapov <potapov.d at gmail.com>

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1589359 13f79535-47bb-0310-9956-ffa450edef68