RFR (14) 8236769: Clarify javadoc of memory access API

[Chris Hegarty]

> On 8 Jan 2020, at 15:52, Maurizio Cimadamore <maurizio.cimadamore at oracle.com> wrote:
> 
> New revision:
> 
> http://cr.openjdk.java.net/~mcimadamore/8236769_v2
> 
> delta from previous:
> 
> http://cr.openjdk.java.net/~mcimadamore/8236769_v2_delta/

LGTM.

-Chris.