RFR (XL): Backport JDK9 Shenandoah to JDK8u

[Roman Kennke]

This huge change backports the current state of JDK9 (minus the last
bunch of patches) to jdk8u:

http://cr.openjdk.java.net/~rkennke/backport-jdk8/webrev.00/

Not sure if this can be reasonably reviewed. ;-)

I checked this line by line and also compared it to our baseline repo (
http://hg.openjdk.java.net/aarch64-port/jdk8u/hotspot/).

The one thing missing is changes in src/share/vm/opto and
src/share/vm/adlc, but Roland is working on those.

I've checked with SPECjvm2008 and jcstress is on the way.
Unfortunately, I could not get the jtreg stuff to work.

Ok to go in?

Roman