Javadoc: Add missing tag.

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1603927 13f79535-47bb-0310-9956-ffa450edef68
Javadoc fixes for Java 8.

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1603928 13f79535-47bb-0310-9956-ffa450edef68