Refactor SerializationFormat::EndWrite and ChunkedIO::Chunk mem mgmt.

SerializationFormat::EndWrite now transfers ownership of the buffer
to the caller instead of doing a memcpy.

ChunkedIO::Chunk is no longer a POD type, hopefully the ctor/dtor
make it easier to manage its associated memory.  It also now
tracks how to deallocate its buffer (i.e. delete vs. free).

src/Val.cc

@@ -92,8 +92,7 @@ Val* Val::Clone() const
 	uinfo.cache = false;
 	Val* clone = Unserialize(&uinfo, type);
 
-	delete [] data;
-
+	free(data);
 	return clone;
 	}