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

[Roman Kennke]

Looks good, but same considerations overall as with the 11u change. :-)

Thanks,
Roman


> 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
>