Query user during kbd macro execution.
With prefix argument, enters recursive edit, reading keyboard
commands even within a kbd macro. You can give different commands
each time the macro executes.
Without prefix argument, asks whether to continue running the macro.
Your options are:
Y Finish this iteration normally and continue with the next.
N Skip the rest of this iteration, and start the next.
RET Stop the macro entirely right now.
C-l Redisplay the screen, then ask again.
C-r Enter recursive edit; ask again when you exit from that. (fn FLAG)