[11u] RFR: 8258077: Using -Xcheck:jni can lead to a double-free after JDK-8193234

[Doerr, Martin]

Hi,

JDK-8258077 is backported to 11.0.11-oracle. I'd like to backport it for parity.
Change almost applies cleanly. I only had to adapt the Copyright year and add #include "utilities/formatBuffer.hpp" manually in jniCheck.cpp.
In order to make the tests work correctly, I had to do the following additional changes:
- Integrate small test fix JDK-8259446 which applies cleanly on top of this change.
- Use System.getProperty("test.nativepath") instead of Utils.TEST_NATIVE_PATH which doesn't exist in 11u.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8258077

Original change:
https://git.openjdk.java.net/jdk/commit/712014c5

11u backport:
http://cr.openjdk.java.net/~mdoerr/8258077_check_jni_11u/webrev.00/

Please review.

Best regards,
Martin