Code review request: 8002273 NMT to report JNI memory leaks when -Xcheck:jni is on

[Zhengyu Gu]

This fix is related to JDK-8001743: Overlapped thread stacks. The cause 
of 8001743 is that, an attached JNI thread exited without detaching the 
thread, so JVM will leak a JavaThread object that attached to the JNI 
thread.

The patch allows NMT to report such case when -Xcheck:jni VM option is 
specified.

http://cr.openjdk.java.net/~zgu/8002273/webrev.00/

Thanks,

-Zhengyu