RFR [11]: 2018-10-05, Bulk backports to sh/jdk11

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk11-20181005/webrev.01/

This backports recent work to sh/jdk11:

 [backport] Make Shenandoah to use ShenandoahOWST only
 [backport] Missed VerifyObjectEquals in VerifyJCStressTest
 [backport] Make sure debug builds fail predictably on safepoint timeout
 [backport] Beef up and parallelize EvilSyncBug test
 [backport] Enable string deduplication in all marking phases
 [backport] Precleaning should use GC workers to do actual work
 [backport] Fix deduplication assert and update comments
 [backport] ShenandoahPushWorkerQueuesScope should subclass ShenandoahPushWorkerScope
 [backport] Handle scenario that not be able to satisfy the request for active workers
 [backport] Fix compilation errors due to missing spaces between string literal and macro
 [backport] Remove dead-weight ShenandoahPrinter
 [backport] Rehash and cleanup usages of ShenandoahHeap::heap()
 [backport] Cleanup up superfluous newlines
 [backport] Cleanup C2 debugging leftovers

Testing: tier3_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey