[8] RFR: Parallel cleaning improvements

[Roman Kennke]

Looks good to me!

Thanks,
Roman

On Mon, 2020-05-25 at 09:30 +0200, Aleksey Shipilev wrote:
> In sh/jdk8, we have gc/shared/parallelCleaning.* that is only used by
> Shenandoah. We did this a long
> time ago thinking we would share this with G1. But, in later
> releases, we have decided to have
> gc/shenandoah/shenandoahParallelCleaning.* instead. sh/jdk11 has it,
> jdk/jdk has it. sh/jdk8 should
> do the same.
> 
> Additionally, there are format specifier problems in
> ~ShenandoahStringSymbolTableUnlinkTask, which
> prevent it to build with C++11 enabled. Those are fixed in a separate
> changeset.
> 
> Webrev:
>   
> https://cr.openjdk.java.net/~shade/shenandoah/8u-parallel-cleaning/webrev.01/
> 
> Testing: hotspot_gc_shenandoah {fastdebug, release}
>