RFR: 8065804: JEP 171: Clarifications/corrections for fence intrinsics

[Martin Buchholz]

Hi folks,

Review carefully - I am trying to learn about fences by explaining them!
I have borrowed some wording from my reviewers!


https://bugs.openjdk.java.net/browse/JDK-8065804
http://cr.openjdk.java.net/~martin/webrevs/openjdk9/fence-intrinsics/