Serialization bug fixes

[Tom Tromey]

>>>>> "Andrew" == Andrew Haley <aph@redhat.com> writes:

Andrew> The good news is that with these fixes, serialization seems to work
Andrew> well, even in a very complex app.

Cool.  We really need to get that serialization test suite online...

Andrew> Also, I needed a native method to walk the stack efficiently to find
Andrew> the caller's class loader.  This will clearly cause problems for
Andrew> Classpath.  I'm hoping that we'll get a cleaner way to do this.

The usual approach is to make a new VM class and put the native method
there.  Look in classpath/vm/reference/ for several examples.

Andrew> 	(depth): New field.

The new fields could use short explanatory comments.

Tom