RFR: Fix and enable suspendible workers by default

[Roman Kennke]

Benchmarks have not shown regressions.

Roman

> Look at this webrev instead. I remove stray includes in 2 non-Shenandoah
> files that slipped in by accident:
> 
> 
> http://cr.openjdk.java.net/~rkennke/fix-enable-susp-workers/webrev.01/
> 
> I'm also currently running benchmarks to check that it doesn't possibly
> regress performance.
> 
> Thanks,
> Roman
> 
>> http://cr.openjdk.java.net/~rkennke/fix-enable-susp-workers/webrev.00/
>>
>> Testing: tier3_gc_shenandoah ok
>> (ShenandoahStrDedupStress times out, but that was pre-existing and
>> doesn't seem related. It appears that we should cut down the test work
>> there, or make it time-based to begin with.)
>>
>> I'll post a jdk8u patch shortly. This requires much more work, because
>> the stuff is not even existent in jdk8u, and STS has slightly different
>> APIs too.
>>
>> Roman
>>
>