RFR 9: 8145459 Cleaner - use Reference.reachabilityFence

[Mandy Chung]

> On Jan 20, 2016, at 7:14 AM, Roger Riggs <Roger.Riggs at oracle.com> wrote:
> 
> Please review this update to the Cleanable implementations to use Reference.reachabilityFence:
> 
> Webrev:
>   http://cr.openjdk.java.net/~rriggs/webrev-fence-8145459/

+1

Mandy