Cherry pick native barrier related changes to shenandoah/jdk

[Zhengyu Gu]

I would like cherry pick native barrier related changes to shenandoah/jdk.

Cherry-pick: 8226823: Adjust BarrierSetC2 for C2 runtime calls
Cherry-pick: 8226822: GC interface for C1 runtime calls
Cherry-pick: 8226695: Shenandoah: Wire C1 and C2 IN_NATIVE barrier
Cherry-pick: 8225483: Shenandoah: Enhance native access barrier

Webrev: 
http://cr.openjdk.java.net/~zgu/shenandoah/native_barriers/webrev.00/

Test:
   in progress.

Thanks,

-Zhengyu