RFR (S): Connection matrix printout, enable in product, reformat

[Aleksey Shipilev]

Hi,

Please see the changes in PrintShenandoahMatrix that enable it in product bits,
and also formats nicely:
 http://cr.openjdk.java.net/~shade/shenandoah/matrix-print/webrev.01/

(Also note VerifyShenandoahMatrix was *not* enabled for product during concmark,
only for mark-compact!)

Testing: hotspot_gc_shenandoah

Sample output:
 https://paste.fedoraproject.org/paste/JtwF3HM4UpPP1cKFgggGgl5M1UNdIGYhyRLivL9gydE=

-Aleksey