Add mod-proxy DNS caching information to the documentation (follow up from users@)

      Members are added to a balancer using

      <directive module="mod_proxy">BalancerMember</directive>.</p>

      <note><title>DNS resolution for origin domains</title>

      <p>DNS resolution happens when the socket to

        the origin domain is created for the first time.

        When connection pooling is used, each backend domain is resolved 

        only once per child process, and reused for all further connections 

        until the child is recycled. This information should to be considered 

        while planning DNS maintenance tasks involving backend domains. 

        Please also check <directive module="mod_proxy">ProxyPass</directive>

        parameters for more details about connection reuse.

        </p>

      </note>

    </section> <!-- /workers -->

    <section id="access"><title>Controlling Access to Your Proxy</title>