RFR: Add support of lzcnt and tzcnt

[Igor Veresov]

>> 
>> Updated webrev: http://cr.openjdk.java.net/~iveresov/lztzcnt/webrev.01/ <http://cr.openjdk.java.net/~iveresov/lztzcnt/webrev.01/>
> 
> Where are the create methods used?
> 
> +    public static AMD64CountLeadingZerosNode create(ValueNode value) {
> +        return new AMD64CountLeadingZerosNode(value);
> +    }
> +    public static AMD64CountTrailingZerosNode create(ValueNode value) {
> +        return new AMD64CountTrailingZerosNode(value);
> +    }

They are not used indeed. I thought it was some sort of convention (is it not?) since they are in BitScan{Froward,Reverse}Nodes but not used as well.

igor