serialVersionUID fixes

[Tom Tromey]

>>>>> "Warren" == Warren Levy <WarrenL@cruzio.com> writes:

Warren> If serialVersionUID is added to all libgcj classes without
Warren> first checking that the correct value is already generated (or
Warren> worse, if it is there and someone later makes changes to the
Warren> libgcj source that masks a different serialVersionUID that
Warren> would be generated), we won't be able to catch true
Warren> serialization divergences.  We'd simply be masking problems.

That's true.  We need a serialization test suite.

Eric Blake's arguments on the Classpath list convinced me to change my
stance on this topic.  It now seems to me that it is too difficult for
us to ensure compatibility in the compiler.

Tom