The version handling in LangUtil has been overhauled
to cope better with post 1.8 releases (JDK9 and JDK10 or 18.3
or whatever they call it). As part of this moved
to treating JDK9 as '9' rather than '1.9'. Also removed
duplicate version processing logic and had that defer to
the one place in LangUtil where we now deal with it.

Includes some generics tidyup in ajdoc. More ajdoc work
is necessary for Java10 because it removes the standard doclet
(old style). However trying to invoke the internal Javadoc
handler in Java10 is failing due to module visibility rules.

Prior to this AspectJ would discard ignore the ClasspathEntry
objects built by JDT and just work with the classpath as a string,
driving the JDT FileSystem to rebuild classpath entries again at
a later date using the string. This is more complex in Java9 because
the string representation was losing whether some entries came in
via modulepath.  ClasspathEntry construction for modulepath entries
is non trivial (since the module-info must be processed).

The new version will cache some of the ClasspathEntry objects (those
built for modulepaths) and do more work on the AspectJ side building
classpath entries in general. It now passes these entries to a
different FileSystem entry point rather than the entry point that
takes a string path.

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.