RFR: Verification should assert complete bitmaps in most phases

[Aleksey Shipilev]

Hi,

Realized that marking data should not become wrong, only less precise. For
either full or partial evac, new objects are allocated after TAMS. Ditto the
regular allocations during all concurrent phases. The only question is Full GC
and generic verification can take cancellation and VM exit paths, I TODO'ed them:

http://cr.openjdk.java.net/~shade/shenandoah/verifier-check-markcomplete/webrev.01/

Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey