simplify ISR bit clearing logic to try to get to the bottom of
why CIA IRQs are getting missed.
add seg led debugging for keyboard and CIA irq bugs
more debug output to help try to find why CIA IRQs often get missed
(didn't work).
try to fix key scanner bug.
rollback to old keymapper that should be working.
put old version of CIA back in the hope that it works properly.
try to fix IRQ driving.