Format of XMS handle table:
Offset	Size	Description	)
 00h	BYTE	??? (01h in HIMEM.SYS v3.09)
 01h	BYTE	size of one handle descriptor
 02h	WORD	number of handles (default = 20h)
 04h	DWORD	pointer to XMS handle array (see #02748)
SeeAlso: #02777