the place where its tricky is with a port that has
JackPortIsTerminal
marked:
        wherever  ---> input port |
and people want to meter the signal arriving at the terminal input
port.
i'll try to think more about how i believe this should be done. i
don't think that connecting/reconnecting is right. 
the obvious solution:
    * client registering terminal input port registers an output port,
        ties the output port to the terminal input port.
    * meter using the output port.
problem: this violates the intended semantics of "terminal port".
--p