Remove obsolete special case.

We no longer allow deserialize() to be called with NULL as an invocant.
Add a Perl binding for Lucy::Util::Freezer.
Increase usage of Freezer.

Introduce Freezer_serialize() and Freezer_deserialize(), which invoke
functions directly for Clownfish core objects while invoking methods on
Lucy objects.

Switch over the Storable hooks to use the new Freezer routines.
Switch Lucy classes away from Obj_Serialize().

Use OutStream methods directly on raw values rather than go through
Obj_Serialize (which will soon be removed).
Add CharBuf-specific routines to Freezer.

Add routines to serialize and deserialize CharBufs specifically to
Freezer, in anticipation of removing such routines from CharBuf.
Use Freezer for CharBuf serialization.

Swap out CharBuf serialization methods for Freezer-based routines.
Remove serialization from Obj and CharBuf.

Remove Serialize() and Deserialize() methods from Obj and CharBuf.
Swap in Freezer for VArray serialization.

Replace VArray serialization methods with Freezer routines.
Swap in Freezer for Num serialization.

Replace serialization methods for all Num subclasses with Freezer
routines.
Swap in Freezer for ByteBuf serialization.

Replace ByteBuf serialization methods with Freezer routines.
Swap in Freezer for Hash serialization.

Replace Hash serialization methods with Freezer routines.
Remove XS binding for Freezer_serialize().
Enable Storable hooks only in Lucy context.

Move the Storable hooks from Clownfish::Obj into individual Lucy classes
which work with Lucy::Util::Freezer.

Define hooks which throw exceptions by default in Clownfish::Obj so that
Storable doesn't mess up trying to serialize a C pointer without
incrementing the refcount, eventually resulting in a double-free.