RFR: Backport recent changes to shenandoah/jdk11

[Roman Kennke]

Thanks!

I integrated your changes, and (trivially) re-based to 11.0.5:

http://cr.openjdk.java.net/~rkennke/backport-jdk11-2019-07-31/webrev.01/

Roman

> On 7/31/19 6:45 PM, Roman Kennke wrote:
>> Full webrev:
>> http://cr.openjdk.java.net/~rkennke/backport-jdk11-2019-07-31/webrev.00/
> 
> *) x86_32 backport is slightly incorrect: there is no support for split .ad files, so new
> shenandoah_x86_32.ad has no effect, and CAS code fails. Fixed like this (apply over "Shenandoah
> x86_32 support" change), passes hotspot_gc_shenandoah with x86_32 afterwards:
>   https://cr.openjdk.java.net/~shade/shenandoah/11u-fix-x86_32.patch
>  Otherwise backports look clean. Can't wait to try it for my apps!
>