Bug 176107 row.__rownum cannot be directly used as group key
Create a table that bind it to a data set. Insert a group. For the Group On field, click on the "..." button to edit the expression, and select from "Availble Column Bindings" | "Table" | "RowNum". This creates a Group On Expression "row.__rownum". The resulting report design cannot be run. It produces error: Column binding "row.__rownum" does not exist. To workaround this, one must create another binding on the table and set its expression to "row.__rownum", then use the new binding as group key. This should not have been necessary. The "__rownum" binding should be implicitly available in all contexts that have a data set. E.g., it should be usable directly as group key, sort key, and in conditional format expressions, etc. Attached is a sample report that produces the error.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/expression/ExpressionCompilerUtil.java
{
	private static final String ROWNUM = "__rownum";
	
	/**
	 * compile the expression
	 * @param expr
	 * @param registry
	 * @param cx
	 * @return
	 */
	public static CompiledExpression compile( String expr, Context cx )
	{
		ExpressionCompiler expressionCompiler = new ExpressionCompiler( );
		expressionCompiler.setDataSetMode( true );
		return expressionCompiler.compile( expr, null, cx );
	}
	/**
	 * 
	 * @param name
	 * @param exprManager
	 * @param scope
	 * @return
	 */
	public static boolean hasColumnRow( String name, ExprManager exprManager )
	{
		if( name == null )
			return false;
		if(name.equals( ROWNUM ))