Bug 176963 Subquery's resultSetExpressions is not consistent between generate and present time.
In generate time, subquery will add the parent query's column binding to its own resultSetExpressions. While in present time, it only has the ones of itself.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/PreparedQuery.java
* @param subQueryName
	 * @return
	 */
	ISubqueryDefinition getSubQueryDefn( String subQueryName )
	{
		return (ISubqueryDefinition) ( (Object[]) subQueryDefnMap.get( subQueryName ) )[0];
	}
	
	/**
	 * @param subQueryName
	 * @return
	 */
	int getSubQueryLevel( String subQueryName )
	{
		return ( (Integer) ( (Object[]) subQueryDefnMap.get( subQueryName ) )[1] ).intValue( );
	}
	
	/**
	 * Executes a subquery
	 * 
	 * @param iterator
	 * @param subQueryName
	 * @param subScope
	 * @return
	 * @throws DataException
	 */
	QueryResults execSubquery( IResultIterator iterator, String subQueryName,
			Scriptable subScope ) throws DataException
	{
		assert subQueryName != null;