RFR: 8154750: Add missing OrderAccess operations to ClassLoaderData lock-free data structures

[Kim Barrett]

> On May 28, 2016, at 12:16 AM, David Holmes <david.holmes at oracle.com> wrote:
> 
> updated webrev: http://cr.openjdk.java.net/~dholmes/8154750/webrev.v3/
> 
> packages_do() uses load_ptr_acquire.
> 
> remove_classes() no longer locks, and asserts that we're at a safepoint.
> 
> hs-nightly testing still under way.

Looks good.