RFR: Cleanup "dirty" mentions

[Roman Kennke]

Am 24.08.2017 um 20:14 schrieb Aleksey Shipilev:
> "Dirty" is very confusing around Shenandoah codebase. Let's rename the uses for what they really
> are. There are no mentions of "dirty" left in gc/shenandoah after this patch:
>   http://cr.openjdk.java.net/~shade/shenandoah/rename-dirty/webrev.01/
>
> Testing: hotspot_gc_shenandoah
>
> Thanks,
> -Aleksey
>
good