hg: shenandoah/jdk: Build fixes: cherry-pick JDK-8200299, JDK-8200423, fix AArch64 build

[ashipile at redhat.com]

Changeset: 58b1ec268475
Author:    shade
Date:      2018-03-27 14:40 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/58b1ec268475

Build fixes: cherry-pick JDK-8200299, JDK-8200423, fix AArch64 build

! src/hotspot/cpu/aarch64/aarch64.ad
! src/hotspot/cpu/x86/sharedRuntime_x86_32.cpp
! src/hotspot/share/prims/privilegedStack.cpp