RFR: 8133646: Internal Error: x86/vm/macroAssembler_x86.cpp:886 DEBUG MESSAGE: StubRoutines::call_stub: threads must correspond

[David Holmes]

Bug: https://bugs.openjdk.java.net/browse/JDK-8133646

webrev: http://cr.openjdk.java.net/~dholmes/8133646/webrev/

The error raised in this bug was not reproducible - it was only seen on 
one machine which was subsequently re-imaged to run Windows. A similar 
Solaris system did not reproduce the bug.

Rather than just close this as not-reproducible I want to push the 
enhanced diagnostics that Vladimir provided here:

http://mail.openjdk.java.net/pipermail/hotspot-dev/2015-August/019667.html

which I've added to the two chunks of code that perform this thread 
sanity check.

Thanks,
David