Fixes bug libgcj/8170
       * java/lang/ClassLoader.java (loadClass): Don't rewrap
       ClassNotFoundException.
       * gnu/java/lang/MainThread.java (run): Chain NoClassDefFoundError.
       * gnu/gcj/runtime/NameFinder.java (remove_interpreter): Removed.
       (remove_internal): New field superceding remove_interpreter.
       (sanitizeStack): Remove all no-package classes starting with "_Jv_".
       Remove no-class methods starting with "_Jv_". And Replace null
       class or method names with the empty string. Stop at either the
       MainThread or a real Thread run() method.
       (newElement): Made static.
       * java/net/URLClassLoader.java (findClass): Throw
       ClassNotFoundExceptions including urls, plus parent using toString().
       (thisString): New field.
       (toString): New method.

From-SVN: r94935