Bug 145022 Provide a utility method to help GUI enhance aggregate on.
DtE will provide a method hasAggregation(String expression) in org.eclipse.birt.core.data.ExpressionUtil, and the return value will be true when the expression is a valid JS expression and it has aggregation defined.
core/org.eclipse.birt.core/src/org/eclipse/birt/core/data/ExpressionParserUtility.java
* @param child
	 * @param tree
	 * @param columnExprList
	 * @throws BirtException
	 */
	private void processChild( Node parent, Node child, ScriptOrFnNode tree,
			List columnExprList ) throws BirtException
	{
		switch ( child.getType( ) )
		{
			case Token.NUMBER :
			case Token.STRING :
			case Token.NULL :
			case Token.TRUE :
			case Token.FALSE :
				break;
			case Token.GETPROP :
			case Token.GETELEM :
				compileDirectColRefExpr( child, tree, columnExprList );
				break;
			case Token.CALL :
				compileAggregateExpr( parent, child, tree, columnExprList );
				break;
			default :
				compileComplexExpr( child, tree, columnExprList );
		}
	}
	/**
	 * compile column reference expression
	 *