RFR [8057744] (process) Synchronize exiting of threads and process [win]

[Ivan Gerasimov]

Hello!

This is a proposal to address issue with wrong exit codes from a Java 
processes on Windows.
In order to avoid a race, calls to _endthread(), exit and _exit() are 
explicitly synchronized.
We allow simultaneous calls to _endthread() by multiple threads.
However, at the time exit() or _exit() is called, no calls to 
_endthread() are allowed.

Some instrumentation added with JDK-8055338 remain in the code to help 
diagnose the failures if they still occur.

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8057744
WEBREV: http://cr.openjdk.java.net/~igerasim/8057744/0/webrev/

Sincerely yours,
Ivan