to send a Message to the reply port specified by the mn_ReplyPort address. Always use ReplyMsg() instead.
1. Places "NT_REPLYMSG" into the mn_Node.ln_Type field. 2. Puts the message to the port specified by mn_ReplyPort.
If mn_ReplyPort is NULL, sets mn_Node.ln_Type to "NT_FREEMSG" (use this feature only with extreme care).