Bug 148755 Add tthe status to the ActivityStackEvent.
If the the event rollback, the ActivityStackEvent status should be ROLL_BACK.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/activity/ActivityStack.java
* completed (the one on the top of the undo stack),or <code>0</code> if
	 * the undo stack is empty.
	 * 
	 * @return the current transaction number
	 */
	public int getCurrentTransNo( )
	{
		if ( undoStack.isEmpty( ) )
			return 0;
		return ( (ActivityRecord) undoStack.lastElement( ) ).getTransNo( );
	}
	/**
	 * Registers a listener. A listener can be registered any number of times,
	 * but will receive each event only once.
	 * <p>
	 * Part of: Notification system.
	 * 
	 * @param obj
	 *            the activity stack listener to register
	 */
	public void addListener( ActivityStackListener obj )
	{
		if ( listeners == null )
			listeners = new ArrayList( );
		if ( obj != null && !listeners.contains( obj ) )
			listeners.add( obj );
	}
	/**
	 * Removes a listener. The listener is removed from the list of listeners.
	 * If the item is not in the list, then the request is silently ignored.