Name
rio_add_inb_buffer — 
     Add buffer to an inbound mailbox queue
 
Arguments
- mport
- 
     Master port containing the inbound mailbox
     
- mbox
- 
     The inbound mailbox number
     
- buffer
- 
     Pointer to the message buffer
     
Description
   Adds a buffer to an inbound mailbox queue for reception. Returns
   0 on success.