[Shenandoah 8u] 8229919: Support JNI Critical functions in object pinning API on x86_32 platforms

[Zhengyu Gu]

I would like backport JDK-8229919 to Shenandoah 8u.
The major difference between original patch and the backport is in tests.


http://cr.openjdk.java.net/~zgu/JDK-8229919/8u/webrev.00/

Test:
   hotspot_gc_shenandoah x86_32 on Linux

Thanks,

-Zhengyu