[AUDIT PATCH] comm cleanup - pconn changes

   Implements the pconn and IdleConnList as storage lists of
Comm::Connection.

   With Comm::Connection the key definition has to change. The old
keying based solely on domain would produce a Connection object whose FD
did not exactly match the remote IP:port selected by the new routing logics.

   I've kept the concept that the pconn key is the details to describe
the remote end of the link used to fetch any given domain. As such its
become much simpler now. Just the remote IP:port from the TCP details
and requested domain (post re-writing) or peer hostname for peer pconn.

  The change also removes the client address from relevance (enhancement
bug fix). Instead we scan the list of pconn going to our desired
remote-end for the local-end details (tcp_outgoing_addr or tproxy IPs)
to pick an exact pconn match (bug fix).

Amos

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