Bug 132805 Set descending to outer group will affect inner group.
Description: Set descending to outer group will affect inner group. Steps to reproduce: 1. New a sample datasource and dataset from orders. 2. Drag the dataset to Layout. 3. Add a group on ordernumber, interval 10, descending. 4. Add another group on orderdate, interval day 2, ascending. 5. Preview. Expected result: Data are grouped correctly. Actual result: Inner group didn't work unless you set outer group's sort to asc.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/expression/ColumnReferenceExpression.java
{
		return m_columnName;
	}
	public int getColumnindex( )
	{
		return m_columnIndex;
	}
	public boolean isIndexed( )
	{
		return ( m_columnIndex != -1 );
	}
	
	public boolean equals(Object other)
	{
		if ( other == null || ! (other instanceof ColumnReferenceExpression))
			return false;
		
		ColumnReferenceExpression expr2 = (ColumnReferenceExpression) other;
		
		if ( m_columnName != null )
			return ( m_columnName.equals( expr2.m_columnName)); 
		else 
			return m_columnIndex == expr2.m_columnIndex;
	}
	
	public int hashCode()
	{
		if ( m_columnName != null )
			return m_columnName.hashCode();
		else