HTTPCLIENT-1393: original request headers do not get copied over in case of multiple redirects

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1518298 13f79535-47bb-0310-9956-ffa450edef68
Added #setHeader methods for completeness

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1518299 13f79535-47bb-0310-9956-ffa450edef68