RFR [8055338]: (process) Add instrumentation to help diagnose JDK-6573254

[Ivan Gerasimov]

Hello everyone!

Here's the third version of the webrev:
http://cr.openjdk.java.net/~igerasim/8055338/2/webrev/

The control build of the previous one was causing a lot of test failures.
This one seems to be innocent enough: no new test failures so far.

Additionally, this version keeps the timing around the thread exit close 
to original, which might be important if we deal with a race.

Sincerely yours,
Ivan