I've upgraded the severity of this bug a bit again, since it seems crazy we have a complete system deadlock marked as "Minor"

Note that we also need a way to detect and recover deadlocked systems.

Since it has become apparent this isn't a system error, we've downgraded the severity of this bug.

This lockup actually isn't the result of a platform or timing bug, it's actually due to the rogue M68000 processor attempting to access the mapped VDP region in the Z80 memory space through the M68000 window into the Z80 bus. This is of course impossible, and causes a lockup on the real hardware. We currently don't have any protection against the same lockup occurring in our bus arbiter however. We need to check if the M68000 is attempting to access back into the M68000 bus through the Z80 bus, and log a critical emulation error if it is. We also need some way to actually handle faulted buses and devices in our system, so that we can properly report these states to the user.