RFR: 8025979 Write test to exercise uninitialized strings from JNI code

[Staffan Larsen]

When JDK-8025922 was fixed, no regression test was added for that issue since jtreg does not support native code. But by using -XX:+ExecuteInternalVMTests it is possible to write a JNI test inside the JVM.

I am a little unsure of where to place the test code - if you have suggestion let me know.

webrev: http://cr.openjdk.java.net/~sla/8025979/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8025979

Thanks,
/Staffan