receiv_rsx DEPRECATED

	receiv_rsx(send_task.i4.r, mess.s.r, dummy.g.v[,status.i2.r])

	This routine will read a 15 word message sent by a previous
	call to SEND_RSX into 'mess'.  The first 2 words contain the
	radix-50 task name of the sender, and the last 13 words contain
	the message.  If 'send_task' is specified, only messages from
	that task will be returned.  This is an RSX emulation routine.

	send_task	sender's task name (radix 50)
	mess		message received (15 words)
	[status]	returned status