fixed memleak in get_ports()

need to free memory allocated by jack_get_ports()
(preferrably using jack_free())
fixed memleak in disconnect() helper-fun

need to free memory allocated by jack_port_get_all_connections()
(preferrably using jack_free())
fixing memleak when construction python lists

seems like PyList_Append() somehow leaks when used with Py_BuildValue().
a better (and leak-safe) solution is to
pre-allocate the list and use PyList_SetItem().
this should also be faster...

reference: http://stackoverflow.com/questions/3512414

this solution has been suggested by Viacheslav Lotsmanov on the sf tracker.