Pls (re)review 6173675/7003271: per-thread memory allocation measurement

[Paul Hohensee]

Thanks to all who reviewed the previous webrev.  Revised versions are here

http://cr.openjdk.java.net/~phh/6173675/webrev.02/
http://cr.openjdk.java.net/~phh/7003271/webrev.02/

The interesting changes are in the library side for 6173675.  In particular,
I've added 3 unit tests.

Thanks for any review,

Paul