RFR: Upstream merge 2018-06-12

[Roman Kennke]

Latest stuff from upstream gives us, among other good stuff, ZGC and
Epsilon GC.

I am merging up to:

changeset:   50895:83fd54252ee4
user:        rriggs
date:        Tue Jun 12 13:07:47 2018 -0400
summary:     8197930: JNI exception pending in initializeEncoding of
jni_util.c

Full list of changes:
http://cr.openjdk.java.net/~rkennke/upstream-merge-2018-06-12/outgoing.txt

Testing: tier3_gc_shenandoah ongoing

Ok (pending clean tests)?