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 filter array given a Listing design element
		 * 
		 * @param listing
		 *            the ListingDesign
		 * @return the filter array
		 */
		public ArrayList createFilters( ListingDesign listing )
		{
			return createFilters( ( (ListingHandle) listing.getHandle( ) )
					.filtersIterator( ) );
		}
		/**
		 * create fileter array given a DataSetHandle
		 * 
		 * @param dataSet
		 *            the DataSetHandle
		 * @return the filer array
		 */
		public ArrayList createFilters( DataSetHandle dataSet )
		{
			return createFilters( dataSet.filtersIterator( ) );
		}
		/**
		 * create filter array given a GroupHandle
		 * 
		 * @param group
		 *            the GroupHandle
		 * @return filter array
		 */
		public ArrayList createFilters( GroupHandle group )