I was wrong in commit 7437 that only one keystroke was working. The problem
was just that I was getting _too_ many events. I wasn't handling key-up
events, and they were entering the buffer, and I was not skipping null
events since the circular buffer is currently considered to be null-terminated.
ex3 isn't done yet; it can only handle 16 events. Apps need to be clearing
the keyboard buffer.
