> Which of these would require changes to allow overloading of input and
> output port names?
> Could those changes be backwards compatible with existing interfaces?
> If so, clients could migrate to this scheme gradually, without
> breaking everything at once.
Well, most obviously 'jack_port_by_name' implies that a name uniquely
identifies a port. The semantics could be changed to allow that not
to be the case, but such changes would break reasonable current uses.