A series of JavaHL fixes on branch 'javahl-1.14-fixes'

I have committed a series of patches for JavaHL on 'javahl-1.14-fixes'
branch. They mostly address crashes when using TunnelAgent, but also fix
some JNI warnings.

The branch also includes automatic tests for problems I fixed. If you
only checkout the first commit of the branch, there will be tests
without any fixes. Adding more commits will gradually fix problems
demonstrated by the new tests.

Now I hope for some attention and reviews :)

Here's how to run JavaHL tests on macOS/Linux:
----------------------------------------------
1) Download [1] JDK and extract it to some folder, for example
/home/user/Downloads/jdk. I have tested with versions 8 and 14, haven't
yet tried the newest version 15.
2) Download [2] JUnit and put .jar to some folder, for example
/home/user/Downloads/junit.
3) During 'configure' SVN build step, pass additional arguments:
     --with-jdk=/home/user/Downloads/jdk
     --with-junit=/home/user/Downloads/junit/junit-4.12.jar
     --enable-javahl
4) Compile with:
     make javahl
5) Run tests with:
     make check-apache-javahl

[1] https://www.oracle.com/java/technologies/javase-jdk14-downloads.html
[2] https://repo1.maven.org/maven2/junit/junit/4.12/junit-4.12.jar
Received on 2020-10-16 19:59:01 CEST