INT 2D - [proposed (v3.3)] - ALTERNATE MULTIPLEX INTERRUPT
	AH = multiplex number
	AL = function
	    00h installation check
		Return: AL = FFh if multiplex number in use
			    CX = version number (CH = major, CL = minor)
			    DX:DI -> signature string (see below) identifying
				    the program using the multiplex number
			AL = 00h if free
	    01h get entry point
		Return: AL = FFh if entry point supported
			    DX:BX -> entry point for bypassing interrupt chain
			AL = 00h if all API calls via INT 2D
	    02h uninstall
		DX:BX = return address for successful uninstall (may be
			ignored by TSR)
		Return: AL = status
			    00h not implemented
			    01h unsuccessful
			    02h can not uninstall yet, will do so when able
			    FFh successful
			return at DX:BX with AL destroyed if successful and
			  TSR honors specific return address
	    03h request pop-up
		Return: AL = status
			    00h not implemented or TSR is not a pop-up
			    01h can not pop up at this time, try again later
			    02h can not pop up yet, will do so when able
			    03h already popped up
			    04h unable to pop up, user intervention required
				BX = standard reason code
				    0000h unknown failure 
				    0001h interrupt chain passes through memory
					  which must be swapped out to pop up
				    0002h swap-in failed
				CX = application's reason code if nonzero
			    FFh TSR popped up and was exited by user
				BX = return value
				    0000h no return value
				    0001h TSR unloaded
				    0002h-00FFh reserved
				    0100h-FFFFh application-dependent
	    04h determine whether chained on interrupt
		BL = interrupt number (except 2Dh)
		Return: AL = status
			    00h not implemented
			    01h unable to determine
			    02h interrupt hooked
			    03h interrupt hooked, address returned
				DX:BX -> TSR's interrupt BL handler
			    FFh interrupt not hooked
		Note:	since INT 2D is known to be hooked, the resident code
			  need not test for BL=2Dh (to minimize its size), and
			  the return value is therefore undefined in that case
	    05h-0Fh reserved for future enhancements
		Return: AL = 00h (not implemented)
	    other  application-dependent
Notes:	programs should not use fixed multiplex numbers; rather, a program
	  should scan all multiplex numbers from 00h to FFh, remembering the
	  first unused multiplex in case the program is not yet installed.
	  For multiplex numbers which are in use, the program should compare
	  the first 16 bytes of the signature string to determine whether it
	  is already installed on that multiplex number.  If not previously
	  installed, it should use the first free multiplex number.
	functions other than 00h are not valid unless a program is installed
	  on the selected multiplex number
	the signature string and description may be used by memory mappers
	  to display the installed programs
	users of this proposal should adhere to the IBM interrupt sharing
	  protocol (see below), which will permit removal of TSRs in
	  arbitrary order and interrupt handler reordering.  All TSRs
	  following this proposal should be removable, though they need not
	  keep the code for removing themselves resident; it is acceptable
	  for a separate program to perform the removal.
	the interrupt number is tentative and may need to be changed before
	  this proposal is finalized
	Please let me know if you choose to follow this proposal.  A list of
	  the private API calls you use would be appreciated, as well.
SeeAlso: INT 2F

Format of signature string:
Offset	Size	Description
 00h  8 BYTEs	blank-padded manufacturer's name (possibly abbreviated)
 08h  8 BYTEs	blank-padded product name
 10h 64 BYTEs	ASCIZ product description (optional, may be a single 00h)
Note:	it is not necessary to reserve a full 64 bytes for the description,
	  just enough to store the actual ASCIZ string

Format of interrupt sharing protocol interrupt handler entry point:
Offset	Size	Description
 00h  2 BYTEs	short jump to actual start of interrupt handler, immediately
		following this data block
 02h	DWORD	address of next handler in chain
 06h	WORD	signature 424Bh
 08h	BYTE	EOI flag
		00h software interrupt or secondary hardware interrupt handler
		80h primary hardware interrupt handler (will issue EOI)
 09h  2 BYTEs	short jump to hardware reset routine
		must point at a valid FAR procedure (may be just RETF)
 0Bh  7 BYTEs	reserved (0)

Signatures known to be in use:
 'TifaWARE' 'RECALL  '	George A. Theall's public domain commandline editor
			and history TSR (v1.2+)
	    'EATMEM  '	restrict available memory for testing programs (v1.1+)
 'heathh  ' 'Monitor '