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 afterGroup
	 * @param cx
	 * @throws DataException 
	 */
	private void prepareExpressions( Collection expressions, int groupLevel,
			boolean afterGroup, boolean isDetailedRow, Context cx ) throws DataException
	{
	    if ( expressions == null )
	        return;
	    
	    AggregateRegistry reg = this.aggrTable.getAggrRegistry( groupLevel,
	    		-1,
				isDetailedRow,
				cx );
	    Iterator it = expressions.iterator();
	    while ( it.hasNext() )
	    {
	        prepareExpression((IBaseExpression) it.next(), groupLevel, cx, reg);
	    }
	}
	
	/**
	 * Prepares one expression
	 * 
	 * @param expr
	 * @param groupLevel
	 * @param cx
	 * @param reg
	 */
	private void prepareExpression( IBaseExpression expr, int groupLevel,