RFR: Add JVMTI notifications to Shenandoah GC pauses

[Roman Kennke]

Am 04.09.2017 um 15:17 schrieb Aleksey Shipilev:
> On 09/04/2017 03:15 PM, Roman Kennke wrote:
>> http://cr.openjdk.java.net/~rkennke/jvmti/webrev.00/
> Okay! But I still do not get why can't we use VM_GC_Operation superclass for this.
>
> -Aleksey
>
>
The superclass does stuff that we don't need/want. It's basically meant
to by used by fully-STW collectors. Both CMS and G1 don't seem to use it
either.

Roman