RFC: jdk10/hs merge

[Aleksey Shipilev]

jdk10/hs is now stabilizing for its own mega-merge. It seems convenient to pull from it now, to
minimize future merges.

The changeset is big:
  425 files changed, 12746 insertions(+), 6732 deletions(-)

Most of that is Graal update. Some merges were required in ReferenceProcessor code that clashes with
additional logging from upstream.

Concerns? Objections?

Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey