more Java changes

[John W. Eaton]

I checked in some changes to the new Java code to move __java__.cc
from a dynamically linked function to be a part of the core
octave_value class hierarchy.  The __java__.cc file already defined an
octave_value class, so it seems simpler to not load it dynamically.
The JVM is still not loaded until the first time a java function is
loaded.

After updating and building, you might want to clean out the __java__
files from your build tree.

jwe