RFR: 8163897: oop_store has unnecessary memory barriers

[Kim Barrett]

> On Oct 23, 2017, at 1:44 AM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
> Please review this change to the oop_store function template, which
> removes some unnecessary memory barriers, moves CMS-specific code into
> GC-specific (though not completely CMS-specific) areas, and cleans up
> the API a bit.  See the CR for more details about the problems.

Due to some miscommunication, Erik O and I have both developed
solutions to this.  Mine is a stand-alone piece of work for me, while
his is some number of changes in a long patch train.  In the interest
of not imposing possibly messy merging on Erik, I'm withdrawing this
RFR and reassigning the bug to him.