Format of Stacker v2+ device driver:
Offset	Size	Description	)
 00h	DWORD	pointer to next driver, offset=FFFFh if last driver
		FFFFh:FFFFh for Stacker Anywhere
 04h	WORD	device attributes (see #01647,#01648)
 06h	WORD	device strategy entry point
 08h	WORD	device interrupt entry point
 0Ah	BYTE	number of subunits (drives) supported by driver
		0 for Stacker Anywhere
 0Bh  7 BYTEs	signature "STAC-CD" for Stacker and Stacker Anywhere
 12h  7 BYTEs	???
 19h	BYTE	always = 01h ?? (Stacker Anywhere points here)
 1Ah	WORD	signature A55Ah (all other Stacker versions point here)
 1Ch	WORD	Stacker version * 64h
		0C8h = 200, 012Ch = 300, 0190h = 400 (also Stacker Anywhere)
 1Eh	WORD	offset of volume-specific information offset table
		(list of WORDs, one per drive, containing offsets to various
 20h 56 BYTEs	n/a
 58h	BYTE	volume number, set after INT 21/AX=4404h, INT 21/AX=4408h
		(use to index into volume-specific info offset table,
		should be set to FFh before and tested for change after)
 59h 19 BYTEs	n/a
 6Ch  4 BYTEs	ASCII string "SWAP"
 70h 26 BYTEs	drive mapping table (one byte for each drive A: through Z:)
		(only used for drives swapped by SSWAP.COM; other drives
		compressed by Stacker can be found with the standard device
		driver header signature (see INT 21/AH=52h)
---Stacker 4, Stacker Anywhere---
 8Ah 40	BYTEs	???
 B2h  4 BYTEs	ASCII string "SWP2"
 B6h 26 BYTEs	drive table ???
 D0h 150 BYTEs	???
166h 60 BYTEs	LZSINFO structure (see #02808 at INT 2F/AX=4A12h)
SeeAlso: #02551,#01646 at INT 21/AH=52h