Multiple changes here:
- annotation unpacking is smarter and if it only needs runtime
  retention annotations it uses reflection and doesn't unpack the
  bytes to discover class level retention annotations.
- Reflection worlds are shared if for the same classloader.

Took the code from the patch submitted by Mario Ivankovits
in bug 520597 and made some improvements to make (hopefully)
better use of memory. Some basic tests added.

On Java9 cannot rely on URLClassLoader being found from which
to determine classpath so use the environment variable. This may
have issues if loaders are being constructed that specifically
deviate from the java.class.path.

If you only let it determine it from the INVOKE instruction this
can make a mistake when using INVOKESTATIC with an interface
target.

Important to ensure we generate it of the right version as it may
end up containing code derived from a particular class that needs
a be run with a certain level of verifier. In this case if
inserting invokestatic targeting a interface method, we need to
be using something later than a java 1.2 level class file.

Issue it due to split packages (see comments in code). Don't want to
debug this further right now, possibly needs a command line flag passing
to the JVM that runs the test, so these tests need forking.

Added test commentary to link it to the code that is causing the
difference in behaviour compared to Java8.

Annotation toString() changes on Java9 so need to include those quotes
in expected output.

Some alternate behaviour added to work better on Java9

I don't want to change that code until I see more evidence of it
misbehaving but I'm having trouble working out why it is there!

JVM improvements seem to reduce the difference.