S11N: Of course singleton's are serializable too
S11N: Minor: move where we leak uninitialized references.
S11N: Use a single class (DeserializingReference) to implement both DeserializableReference and RealizableReference, which simplifies things a bit.
S11N: add a less-than-perfact way to prevent leakage of partially constructed objects in the face of exceptions during deserialization.
S11N: A small test of the DeserializingReference