RFC: jdk/jdk10 -> sh/jdk10 merge

[Aleksey Shipilev]

Hi,

We have prepared a (very painful) merge from jdk/jdk to sh/jdk10:
  2991 files changed, 130102 insertions(+), 177022 deletions(-)

...where Hotspot changes are:
   671 files changed, 14242 insertions(+), 24451 deletions(-)

If you are curious, these are the changes that merge brings:
  http://cr.openjdk.java.net/~shade/shenandoah/merge-jdk-jdk-2017-11-22/hotspot.patch

Notable changes: suspendible thread set handling is better, code cache roots handling is better
(still needs to be hooked up to Shenandoah better), CLDG roots handling is better (need to revisit
how Shenandoah uses that facility), all sorts of method renames and cleanups (e.g. cmpxchg_ptr ->
cmpxchg).

Unless there are strong concerns about this, I'd like to push and get more regular testing done on
new sh/jdk10. It is possible it regresses something our acceptance tests are not covering.

Caveat: sh/jdk10 now requires JDK 9 as bootstrap JDK. Old jtreg still works.

Testing: hotspot_gc_shenandoah {fastdebug|release}, specjvm with verification

Thanks,
-Aleksey