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	AddIntServer -- add an interrupt server to a system server chain

	AddIntServer(intNum, interrupt)
		     D0-0:4  A1

	void AddIntServer(ULONG, struct Interrupt *);

	This function adds a new interrupt server to a given server chain.
	The node is located on the chain in a priority dependent position.
	If this is the first server on a particular chain, interrupts will
	be enabled for that chain.

	Each link in the chain will be called in priority order until the
	chain ends or one of the servers returns with the 68000's Z condition
	code clear (indicating non-zero).  Servers on the chain should return
	with the Z flag clear if the interrupt was specifically for that
	server, and no one else.  VERTB servers should always return Z set.
	(Take care with High Level Language servers, the language may not
	have a mechanism for reliably setting the Z flag on exit).

	Servers are called with the following register conventions:

	    D0 - scratch
	    D1 - scratch

	    A0 - scratch
	    A1 - server is_Data pointer (scratch)

	    A5 - jump vector register (scratch)
	    A6 - scratch

	    all other registers must be preserved

	intNum - the Paula interrupt bit number (0 through 14). Processor
		 level seven interrupts (NMI) are encoded as intNum 15.
		 The PORTS, COPER, VERTB, EXTER and NMI interrupts are
		 set up as server chains.
	interrupt - pointer to an Interrupt structure.
		 By convention, the LN_NAME of the interrupt structure must
		 point a descriptive string so that other users may
		 identify who currently has control of the interrupt.

	Some compilers or assemblers may optimize code in unexpected ways,
	affecting the conditions codes returned from the function.  Watch
	out for a "MOVEM" instruction (which does not affect the condition
	codes) turning into "MOVE" (which does).

	The graphics library's VBLANK server, and some user code, currently
	assume that address register A0 will contain a pointer to the custom
	chips. If you add a server at a priority of 10 or greater, you must
	compensate for this by providing the expected value ($DFF000).

	RemIntServer(), SetIntVector(), hardware/intbits.i,exec/interrupts.i

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