RFR(M): 8209420: Track membars for volatile accesses so they can be properly optimized

[Roland Westrelin]

>> 1) the store saves a value that was just loaded from the same address
>
> That doesn't sound right.  If the accesses are volatile then every
> core should see them in the same total order.  This IRIW problem should
> be detectable in jcstress.  I'll do a run.

As replied to Andrew D. only volatile stores to non escaping objects
should be affected. FWIW, I did a full jcstress run.

Roland.