If the sim is running slower than 60Hz, it was using the frame limiter
to not apply because no frame was drawn, and so it would end up running
at full speed. Minifb can save the last frame without cloning it, and
redraw the same frame if no new frame is ready, which allows the limiter
to still delay the next frame, so slower speeds work. This was also
preventing things that didn't update the screen from allowing inputs
including escape to have any effect
I wanted to make this a bit more modular, so it's easier in theory to
write external crates that can reuse bits, and selectively compile in
bits, such as adding new systems or new cpu implementations
transistor