INT 21 - Windows95 - LONG FILENAME - TERMINATE SUBST                            
	AX = 71AAh
	BH = 01h
	BL = drive number (01h = A:, etc.)
Return: CF clear if successful
	CF set on error
	    AX = error code (see #01680)
		7100h if function not supported
Note:	the specified drive number may not be 00h (default), and presumably not
	  the current drive either
SeeAlso: AX=71AAh/BH=00h,AX=71AAh/BH=02h,INT 2F/AX=1000h,#01643