Received immediate message callback delegate.

C# |
public delegate int LBMImmediateMessageCallback( Object cbArg, LBMMessage lbmmsg )

- cbArg (Object)
- Callback object token
- lbmmsg (LBMMessage)
- LBMMessage object encapsulating the received message

-1 indicates that the message could not be received and should be redelivered.
(Note: if multiple callbacks are registered, a -1 return from any callback will cause the
message to be redelivered to all the callbacks.)