1 DN5LOOP
 This routine will test the specified DECnet address with 
 an APPLICATION LOOPBACK (Mirror) packet.

2 Input
	P1	value of 2 byte DECnet address of target node
	P2 	.address of .long  where reponse time is written
2 Output
 The average response time of 10 loops is written to P2 (100th sec units)
2 Return
	SS$_NORMAL	All Requested loops were succesful
	SS$_UNREACHABLE	Failed to receive loop response from target
	SS$_ACCVIO	Can' read input params or can't write outp field
