RFR: Bulk backport to shenandoah/jdk11

[Roman Kennke]

>> Notable changeset is:
>> 8217717: ZGC: Broken oop map in C1 load barrier stub
> 
> I am not sure we can accept cherry-picked / double patches in sh/jdk11, which serves as our
> integration repository. Is there really no way to make this Shenandoah-specific for a while, until
> the upstream fix arrives via 11u-updates?

Alright, I folded the fixed implementation of resolve_address() into
ShenandoahBarrierSet (as resolve_address_super(), with added TODO
comment there). The only remaining & required shared change is
BarrierSetC1::clear_decorators() which is a harmless 1-liner.

Changesets:
http://cr.openjdk.java.net/~rkennke/backport-shjdk11-2020-01-13/changesets-01.txt

Webrev:
http://cr.openjdk.java.net/~rkennke/backport-shjdk11-2020-01-13/webrev.01/

Good now?

Roman