EFUN: set_heart_beat

SYNTAX:
int set_heart_beat( hb_flag );
  int hb_flag;

DESCRIPTION:
With set_heart_beat you can enable or disable a heart_beat. If the
heart_beat is not needed for the moment, then do disable it. This
will reduce the system overhead (and lag!) drastically. To enable
a heart_beat 'hb_flag' must be 1, and 0 to disable the heart_beat again.
If enabled the local function heart_beat() will be called every 2 seconds.

RETURN VALUE:
Set_heart_beat returns 1 for success, and 0 for failure. Specifically,
it will fail if the heart_beat function has been disabled due to a
run time error in the object.

SEE ALSO:
heart_beat [lfun]
call_out

EXAMPLE:
An aggressive monster...
object enemy;

void init() {
  if( aggressive ) {
    enemy = previous_object();
    set_heart_beat( 1 );
}

void heart_beat() {
  if( present( enemy, environment( this_object() ) ) )
    attack( enemy );
}
// This will start a heart_beat timed attack if a player enters the room.
