RFR: Rework ClassUnloading* flags handling

[Roman Kennke]

Am 18.05.2018 um 16:26 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/class-unload-rework/webrev.01/
> 
> We have lost some of this during upstream merges, and we have not noticed because no tests verified
> how we handle ClassUnloading* flags. This patch makes sure ClassUnloading* flags are treated well by
> Shenandoah in every mode. New tests capture the intended behavior, including OOME when class
> unloading is disabled and classes leak.
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
> 

One question: it does not disable concurrent class unloading by default,
right? I'm asking because if I understood correctly, you meant to do that?

Roman