Bug 177504 Engine doesn't provide SubQuery for extended item
Engine doesn't provide SubQuery for extended item, so chart can't use container's binding to execute the query. If possible, engine could provide an option for extended item to choose whether engine could create the query, so extended item won't create SubQuery by itself.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/extension/internal/ExtensionManager.java
return object;
		}
		catch(FrameworkException ex)
		{
			if (logger.isLoggable( Level.WARNING ))
			{
				logger.log(Level.WARNING, "Can not instantiate class {0} with property {1}.",	 
						new String[] {config.getAttribute("class"), property} );	
			}
			ex.printStackTrace();
		}
		return null;
	}
	/**
	 * load report item generation extension definitions 
	 */
	protected void loadGenerationExtensionDefns()
	{
		IExtensionRegistry registry = Platform.getExtensionRegistry(); 
		IExtensionPoint extPoint = registry.getExtensionPoint(EXTENSION_POINT_GENERATION);
		if(extPoint==null)
			return;
		IExtension[] exts = extPoint.getExtensions();
		logger.log(Level.FINE, "Start load extension point: {0}", EXTENSION_POINT_GENERATION); 
		for (int i = 0; i < exts.length; i++)
		{
			IConfigurationElement[] configs = exts[i].getConfigurationElements();
			for (int j = 0; j < configs.length; j++)
			{
				String itemName = configs[j].getAttribute("name");