INT 2F - DR DOS 6.0+ IBMBIO.COM - REGISTER ROOT OF UPPER MEMORY LINK            
	AX = 12FFh
	BX = 0009h
	DX = new value for root segment of upper memory link
Return: AX = 0000h if supported
	ES:BX modified
Notes:	the DX value is stored at offset 66h in SYSVARS (see INT 21h/AH=52h)
	  and offset 18h in the Novell DOS 7 internal variable table
	  (see INT 21/AX=4458h)
	This API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. is provided by IBMBIO.COM for the initialization phase
	  of drivers loaded via DEVICE=/HIDEVICE=/DEVICEHIGH= directives and
	  is only available during these short time intervals.  It is probably
	  initiated by the Novell DOS 7+ EMM386.EXE.
	this function has apparently been supported since DR DOS 6.0 "Buxton"
	  of 1991/03/19
	for Novell DOS 7, ES:BX points at the internal variable table DRDAT,
	  but this may change in future releases