RFR: Degenerated GC: rename enum, report degen reasons in stats

[Roman Kennke]

Am 06.03.2018 um 10:25 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/degenerated-logs/webrev.01/
> 
> The major improvement is classifying Degenerated GC reasons in -Xlog:gc+stats. Also renamed the enum
> to be shorter.
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
> 

Looks good. And useful.

Thanks, Roman