RFR: [11] Make Shenandoah buildable on all platforms

[Roman Kennke]

Am 24.04.2018 um 14:10 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/alt-platforms-11/webrev.01/
> 
> This makes current sh/jdk build without issues on (hopefully) all OpenJDK platforms. It does not add
> support on those platforms, but merely enables the builds. I made SPARC and Zero changes blindly.
> This is 11-specific patch, backports would need to be fixed separately.
> 
> Testing: arm32, ppc64el, s390x cross-builds
> 
> Thanks,
> -Aleksey
> 

Wow cool! Patch looks good.

I guess as soon as the GC barrier interfaces are complete, it'll make
sense to find somebody to fill in the remaining parts.

Roman