RFR [11], 2018-07-09, Bulk backports to sh/jdk11

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk11-20180709/webrev.01/

This backports recent fixes and improvements to sh/jdk11:

 [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] Traversal pacing is too aggressive: live data is way lower than free
 [backport] Cleanup UseShenandoahOWST blocks

Testing: tier3_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey