RFR [8], 2018-07-09, Bulk backports to sh/jdk8

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20180709/webrev.01/

This backports recent fixes and improvements to sh/jdk8:

 [backport] CollectedHeap::max_tlab_size is measured in words
 [backport] Make in-cset checks use signed bytes to match C2 better
 [backport] Constify ShHeapRegionSet and ShCollectionSet
 [backport] Application pacing precision fixes
 [backport] Adaptive CSet selection overshoots max-CSet
 [backport] StringInternCleanup times out
 [backport] Wrap worker id in thread local worker session
 [backport] Non-cancellable mark loops should have sensible stride
 [backport] Forceful SATB buffer flushes should be time-periodic, not traffic-dependent
 [backport] Verify global and local gc-state status
 [backport] Full GC should not always update references
 [backport] Remove safe_equals()
 [backport] Concurrent uncommit should be recorded as GC event
 [backport] Uncommit should relinquish the heap lock regularly
 [backport] Cleanup UseShenandoahOWST blocks

Testing: hotspot_tier3_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey