- If there is no VMWare backdoor, don't allocate memory for it.
- Remove the "unsupported" state, instead just don't instantiate.
- Move the command-line parsing from init to the driver.
- Move mouse packet reception from PS2MouseDevice to VMWareBackdoor.
We add this feature together with the VMWareBackdoor class.
VMWareBackdoor class is responsible for enabling the vmmouse, and then
controlling it from the PS2 mouse IRQ handler.