- incomplete, it didn't account for the CLEAR @-code which is only handled here
- caused side-effects in that any Baja PRINT function call with a single line
  that contained any  ^A or @-codes would reset the console abort indication
  flag (SS_ABORT).
  Observed: hitting Ctrl-C at while executing the yesnobar.bin or noyesbar.bin
  would leave "Yes Yes No" on the console, for example.
  Solution: use the tos (top-of-screen) state before/after the call to ctrl_a()
  or show_atcode() to determine if the reset-abort hack should be applied.