Function:   GetDir()

               GetDir returns the current directory for a
               specified drive. A similar function exists in
               Extend, this one uses another parameter function,
               more compatible with the DiskTotal(), GetDisk()
               etc.. functions of the Expand library. Extend's
               CurDir() accepts a character as an argument,
               GetDir() uses a numerical value.

   Syntax:     GetDir([<nDisk>]) --> cCurDir

   Arguments:  <nDisk> indicates the drive, 0 or None means
               current, 1 is A: etc..

   Returns:    A character string indicating the current
               directory, there's no leading \ nor is there a
               drive letter, so empty string means Root is
               current.

   Usage:      if GetDir() <> ''
                  ChDir('..')
                  * Change to parent directory..
               end