INT 7F - Alloy MW386 - SET TERMINAL DRIVER FOR ANOTHER USER                     
	AH = 39h
	AL = new terminal driver number
	    FFh dummy driver
	    FEh current driver
	    FDh load new driver
		DS:SI -> new driver
	DL = user number (FFh = caller)
	DH = machine number if DL <> FFh
Return: CF set if invalid user number
	CF clear if successful
Notes:	only available to supervisors
	the new driver number will not take effect until the user is rebooted
SeeAlso: AH=38h