INT 21 U - DOS 4.0 internal - IFSsee Installable File System IOCTL
	AH = 6Bh
	AL = subfunction
	    00h ???
		DS:SI -> Current Directory StructureThe data record used by DOS to keep track of the current directory on a drive; whether the drive is valid, network, SUBSTituted, or JOINed; and other pertinent information.  See also INT 21h Function 52h.???
		CL = drive (1=A:)
	    01h ???
		DS:SI -> ???
		CL = file handle???
	    02h ???
		DS:SI -> Current Directory StructureThe data record used by DOS to keep track of the current directory on a drive; whether the drive is valid, network, SUBSTituted, or JOINed; and other pertinent information.  See also INT 21h Function 52h.???
		DI = ???
		CX = drive (1=A:)
Return: CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)
	CF clear if successful
Notes:	passed through to INT 2F/AX=112Fh with AX on top of stack
	Novell DOS 7 Update 15 returns CF set/AX=0001h (invalid function)
SeeAlso: AH=6Bh"DOS 5",INT 2F/AX=112Fh
                                                                                

INT 21 U - DOS 5+ - NULL FUNCTION                                               
	AH = 6Bh
Return: AL = 00h
Note:	this function does nothing and returns immediately
SeeAlso: AH=6Bh"DOS 4"