hg: shenandoah/jdk9/hotspot: Move shenandoah oop CAS to MacroAssembler, cleanup, document, and optimize it a little.

[ashipile at redhat.com]

Changeset: 0a60700ab638
Author:    shade
Date:      2016-09-29 10:33 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk9/hotspot/rev/0a60700ab638

Move shenandoah oop CAS to MacroAssembler, cleanup, document, and optimize it a little.

! src/cpu/x86/vm/macroAssembler_x86.cpp
! src/cpu/x86/vm/macroAssembler_x86.hpp
! src/cpu/x86/vm/x86_64.ad
+ test/gc/shenandoah/cas/ReferenceCAS.java