Add support for using versionned symbols

[smortex]

This is a follow-up to jnr/jffi#66 and use the new API to make it possible to access versioned symbols in a shared library.

Please note that I usually don't do Java. Instructions for improvements are welcome so that I can update the PR!

With my knowledge of Java, I could not find a better way to access two versions of the same function by assigning a new unique name for each function name and version combinaison. I therefore added 2 annotations that can be used on a function to indicate the actual function name (Function annotation) and the version to use (Version annotation).

The test suite therefore tests:

• A function with it's normal exported name without setting a version: answer;
• A function with it's normal exported name setting a specific version: answer (in another class);
• An internal functions for the old implementation without setting a version: old_answer;
• An internal functions for the new implementation without setting a version: new_answer;
• Two function with a random name using a custom name (the normally used exported name) and specific versions: answer_1_0 and answer_1_1.

CI failures are expected at this stage since jffi changes have not been merged yet.

[headius]

Ok, waking this up again since it came up on #133.

The limiting factor here is still rebuilding everything. It may be possible to build only for some platforms if there's a way to guard against calling the new native binding, so for example we would use the existing Foreign.getVersion to check whether the library has been updated.

I need to double-check that, though, since I don't remember when JNI tries to actually bind the native functions in a given class. I think it's lazy.