RFR (S): 8151614: Improve logging in concurrent mark code

[Thomas Schatzl]

Hi Bengt,

On Mon, 2016-03-14 at 13:39 +0100, Bengt Rutisson wrote:
> Hi Thomas,
> 
> I like the "Concurrent Cycle" logging.
> 
> The change looks good to me.
> 

  thanks for your review.

Thomas