RFR (S): [8u] Sync up vmOperations_shenandoah.* against JDK 9

[Aleksey Shipilev]

Hi,

This makes vmOperations_shenandoah_* match JDK 9 versions closely:
 http://cr.openjdk.java.net/~shade/shenandoah/jdk9-8u/vmops-backport/webrev.01/

The difference is now minimal: _pending_list_basic_lock, and GCId.

Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey