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/data/dte/ReportQueryBuilder.java
* create input parameter bindings
		 * 
		 * @param iter
		 *            parameter bindings iterator
		 * @return a list of input parameter bindings
		 */
		protected ArrayList createParamBindings( Iterator iter )
		{
			ArrayList list = new ArrayList( );
			if ( iter != null )
			{
				while ( iter.hasNext( ) )
				{
					ParamBindingHandle modelParamBinding = (ParamBindingHandle) iter
							.next( );
					IInputParameterBinding binding = createParamBinding( modelParamBinding );
					if ( binding != null )
					{
						list.add( binding );
					}
				}
			}
			return list;
		}
		/**
		 * converts interval string values to integer values
		 */
		protected int parseInterval( String interval )
		{
			if ( DesignChoiceConstants.INTERVAL_YEAR.equals( interval ) )