Appends an arbitrary .NET Object to the message, with a name.
The object will be encoded in a binary field, using the standard
serialization mechanism. Therefore, the object passed to this
method must implement the Serializable interface. Note that any
objects to be serialized must not only themselves be implemented
Serializable, but all of the classes they extend must be Serializable.
This object will only be useful to receiving clients in .NET. C
clients will receive a binary field which may be forwarded to
other .NET clients.