OvrGetRetry function

  DECLARATION:  OvrGetRetry

      PURPOSE:  Returns the size of probation area in the overlay buffer

         UNIT:  Overlay

  RESULT TYPE:  LongInt

      REMARKS:  Any free space in the overlay buffer is considered to be
                part of the probation area.  The probation area size is set
                with the OvrSetRetry procedure, and this function is used
                to return the value last set using that procedure.