CD insert detection is unimplemented

From the [original project](https://github.com/cebix/macemu)'s [`BasiliskII/src/MacOSX/ToDo.html`](https://github.com/cebix/macemu/blob/0a7fe2eaf8e88a458836c3ec1f382906b253d85a/BasiliskII/src/MacOSX/ToDo.html):

> CD insert detection. At the moment, if a CD isn't there when the emulator boots, or if you change CDs, it will never know. I don't know how to register with the OS for disk insertion and mount events. (Gwenolé rewrote the CD code, and it should poll for new disks, but it don't work for me. I must be doing something wrong!)

No further information is available; it's also possible that this issue has been addressed in the time since that 2007-07-14 revision.