re PR libgcj/2237 (serialization doesn't throw exception on failure)

re PR libgcj/2237 (serialization doesn't throw exception on failure)

	Fix PR libgcj/2237:
	* java/io/ObjectStreamClass.java (setClass): Calculate
	serialVersionUID for local class and compare it against the UID
	from the Object Stream. Throw InvalidClassException upon mismatch.
	(setUID): Renamed to...
	(getClassUID): this. Return the calculated class UID rather than
	setting uid field directly.
	(getDefinedSUID): Removed.
	* java/io/ObjectInputStream.java (resolveClass): Use the
	three-argument Class.forName().
	* java/io/InvalidClassException (toString): Don't include classname in
	result if it is null.

From-SVN: r41567