Format of XMS XDI structure:
Offset	Size	Description	)
 00h	DWORD	pointer to 10-byte record???
 04h	DWORD	pointer to next XMS XDI structure
 08h	WORD	mapping context
 0Ah	BYTE	???
 0Bh  5 BYTEs	XMS entry point to return for INT 2F/AX=4310h"XMS"
		(FAR jump to next field)
 10h  6 BYTEs	FAR handler for XMS driver entry point
		(consists of a FAR CALL followed by RETF)