RFR: Upstream merge from jdk/jdk 2018-07-06

[Roman Kennke]

Let's merge latest upstream jdk/jdk into shenandoah/jdk. Starting with
this merge, I'll always merge up to next relevant tag. This merges up to:

changeset:   51388:dea7ce62c7b0
user:        jwilhelm
date:        Thu Jul 05 13:31:04 2018 +0200
summary:     Added tag jdk-12+1 for changeset 00b16d0457e4

And starting with this merge, I'll add corresponding shenandoah-tags
too: shenandoah-jdk-12+1 .

(I also merged at intermediate jdk-12+0 and added corresponding
shenandoah-jdk-12+0)

Testing: tier3_gc_hotspot

List of changesets:

http://cr.openjdk.java.net/~rkennke/jdk-upstream-merge-2018-07-06/outgoing.txt


Ok?