procedure wait(efn:event_flag;
                   Count: Integer;
                   Units: Time_Unit
  		);
   EXTERNAL;
{*USER*
 Procedure Wait issues a MRKT directive, followed by a STOP for efn.
The result is to stop the calling task for the specified duration.
The STOP is not issued if the MRKT directive fails. Works with
all event flags.
 Directive status is available in $DSW on return.
 Companion procedure WAITW issues a Wait for efn, rather than a
STOP for efn.
}