Fexpand function

  DECLARATION:  Fexpand(Path : PathStr)

      PURPOSE:  Expands a file name to a fully qualified file name

         UNIT:  The DOS unit

  RESULT TYPE:  PathStr

      REMARKS:  The resulting PathStr is converted to uppercase and
                consists of a drive letter, a colon, a root relative
                directory path, and a file name.  Embedded '.' and '..'
                directory references are removed.

                NOTE:  The PathStr type is defined in the DOS Unit
                       as String[79]