RFR (M): 8201492: Properly implement non-contiguous generations for reference discovery

[Kim Barrett]

> On May 2, 2018, at 5:36 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Webrevs:
> http://cr.openjdk.java.net/~tschatzl/8201492/webrev.2 (full)
> http://cr.openjdk.java.net/~tschatzl/8201492/webrev.1_to_2 (diff)
> 
> Thanks,
>  Thomas

Looks good.