RFR: Print heap usage info on partial GC logs

[Roman Kennke]

We're not printing heap usage infos in the logs for partial GC pauses.
It's interesting though, because we're reclaiming memory in the
post-partial-GC pause.

http://cr.openjdk.java.net/~rkennke/partial-heap-info/webrev.00/
<http://cr.openjdk.java.net/%7Erkennke/partial-heap-info/webrev.00/>

Roman