[aarch64-port-dev ] RFR: Bulk import from Shenandoah

[Roman Kennke]

I would like to bulk-import some changes from Shenandoah/JDK8u:

http://cr.openjdk.java.net/~rkennke/aarch64-bulk-import-shenandoah-2017-08-21/webrev.00/
<http://cr.openjdk.java.net/%7Erkennke/aarch64-bulk-import-shenandoah-2017-08-21/webrev.00/>

It is made of 26 changes, squashed into one bulk change. It's mostly
backports of stuff that has baked in jdk9 and jdk10 dev repos, and some
jdk8 specific fixes and added tests. It's all gone through our own
testing, and doesn't touch anything non-shenandoah.

The reason why we're doing bulk import instead of single-changeset
import as we did last time is that it makes it easier to merge the
import back into Shenandoah. I got a whole lot of problems this time
with sorting out conflicts from last merge's transplanted changesets.

Ok to push?

Roman