hg: shenandoah/jdk11: Fix ShenandoahBarrierSetC2::enqueue_useful_gc_barrier (part of JDK-8212611)

[shade at redhat.com]

Changeset: 6e1a7d16773c
Author:    roland
Date:      2018-10-17 10:19 +0200
URL:       https://hg.openjdk.java.net/shenandoah/jdk11/rev/6e1a7d16773c

Fix ShenandoahBarrierSetC2::enqueue_useful_gc_barrier (part of JDK-8212611)

! src/hotspot/share/gc/shared/c2/barrierSetC2.hpp
! src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp
! src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.hpp
! src/hotspot/share/gc/z/c2/zBarrierSetC2.cpp
! src/hotspot/share/gc/z/c2/zBarrierSetC2.hpp
! src/hotspot/share/opto/node.cpp
! src/hotspot/share/opto/phaseX.cpp