RFR: 8236778: Add Atomic::fetch_and_add

[Kim Barrett]

> On Jan 9, 2020, at 8:50 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
>> On Jan 9, 2020, at 5:17 PM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
>> 
>> Updated webrev:
>> https://cr.openjdk.java.net/~stefank/8236778/webrev.02.delta
>> https://cr.openjdk.java.net/~stefank/8236778/webrev.02
> 
> Looks good except for a couple more comment tweaks described below.

BTW, I don’t need a new webrev for those additional comment tweaks.