RFR 8207205 [lworld] Unsafe/VarHandle read-modify-write value accessors

[Paul Sandoz]

Hi,

This patch fills out the remaining (and not very efficient) support in Unsafe/VarHandle for read-modify-write value accessors:

  http://cr.openjdk.java.net/~psandoz/valhalla/vh-value-accessors/webrev/ <http://cr.openjdk.java.net/~psandoz/valhalla/vh-value-accessors/webrev/>

I plan to follow up separately with tests, which may take a little more time to tease apart the current test infrastructure, plus i may not get to it this week before going on vacation.

Paul.