Add ap_proxy_connect_backend that will replace

ap_proxy_connect_to_backend. It uses worker params for setting socket
options and checks for conection's connect status.
It works both on empty and acquired connections.

Submitted by: mturk


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@104595 13f79535-47bb-0310-9956-ffa450edef68