RFR: Merge from upstream jdk/jdk

[Roman Kennke]

I prepared merge from upstream jdk/jdk repository to shenandoah/jdk. It
brings us up to:

changeset:   49393:48452579de86
user:        sherman
date:        Tue Mar 13 00:22:14 2018 -0700
summary:     8196748: tools/jar tests need to tolerate unrelated warnings


Notable changes that affect us (and reduce our upstream exposure):
- thread initialization and teardown that used to init and flush SATB
buffers and gc_state flags has moved to GC specific hooks via
ShenandoahBarrierSet::on_thread_attach() and
ShenandoahBarrierSet::on_thread_detach()
- we now have a resolve() method in Access API that is intended to
ensure an oop can be safely used (read+write). It's used for the _addr()
accessors in typeArrayOoop and a few other places.
- arraycopy stuff in the runtime has been streamlined and fixed

http://cr.openjdk.java.net/~rkennke/merge-2018-03-14/webrev.00/

(give it some little time to finish uploading)

Passes: hotspot_gc_shenandoah (fastdebug/release) and specjvm
(fastdebug/release)

Ok to push?

Roman