040706  Servers can be assigned different weights to account for
        differing capacity. New -W command-line option. New penctl
        commands:
        server S weight W       (assign weight to server)
        weight                  (use weight for server selection)
        no weight               (do not use weight for server selection)

        Cleaned up the logic in add_client so the weighted server
        selection can be used without client tracking.

        Released 0.15.0.