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
* Clears the record stack.
	 */
	public void flush( )
	{
		destroyRecords( redoStack );
		destroyRecords( undoStack );
	}
	/**
	 * Private method to remove all records on a stack.
	 * 
	 * @param stack
	 */
	private void destroyRecords( Stack stack )
	{
		Iterator iter = stack.iterator( );
		while ( iter.hasNext( ) )
		{
			ActivityRecord cmd = (ActivityRecord) iter.next( );
			assert cmd.getState( ) != ActivityRecord.DISCARD_STATE;
			cmd.destroy( );
			cmd.setState( ActivityRecord.DISCARD_STATE );
		}
		stack.removeAllElements( );
	}
	/**
	 * Sets the stack size limit. If the stack already exceeds the new limit
	 * then the excess records are flushed.
	 * 
	 * @param limit
	 *            The new stack size limit.