RFR: Upstream merge from jdk/jdk

[Roman Kennke]

>> First merge from upstream in new world order. Merge was 0 conflict and
>> trivial, everything builds+ runs just fine. It merges up to tag jdk-13+2
>>
>> http://cr.openjdk.java.net/~rkennke/upstream-jdk13-merge-2019-01-08/outgoing.txt
>>
>> Testing: hotspot_gc_shenandoah
>>
>> Ok?
> 
> OK, but sh/jdk12 should fork first.

I don't think this is necessary. sh/jdk12 will be forked from jdk/jdk12
which has (almost) the same Shenandoah as we have in sh/jdk. Shenandoah
itself is not yet moving in any branch.

Roman