INT 21 - DOS 2+ - "LSEEK" - SET CURRENT FILE POSITION
        AH = 42h
        AL = origin of move
            00h start of file
            01h current file position
            02h end of file
        BX = file handle
        CX:DX = offset from origin of new file position
Return: CF clear if successful
            DX:AX = new file position in bytes from start of file
        CF set on error
            AX = error code (01h,06h) (see AH=59h)
Notes:  for origins 01h and 02h, the pointer may be positioned before the
          start of the file; no error is returned in that case, but subsequent
          attempts at I/O will produce errors
        if the new position is beyond the current end of file, the file will
          be extended by the next write (see AH=40h)
SeeAlso: INT 2F/AX=1228h