hg: shenandoah/jdk: Make in-cset checks use signed bytes to match C2 better

[ashipile at redhat.com]

Changeset: b1bc743e6784
Author:    shade
Date:      2018-06-26 18:43 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/b1bc743e6784

Make in-cset checks use signed bytes to match C2 better

! src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp