RFR(S): 8173335: Improve logging for j.l.ref.reference processing

[Thomas Schatzl]

> Hi Aleksey and Thomas,
> 
> I expected I would update the webrev when I replied to Aleksey.
> Thomas mentioned about no need for extra webrev, but as I replied to 
> Aleksey for the next webrev, here it is.

> 
[...]
>
> http://cr.openjdk.java.net/~sangheki/8173335/webrev.5/ (full)
> http://cr.openjdk.java.net/~sangheki/8173335/webrev.5_to_4/
> (incremental)

Still looks good.

  Thomas