FSearch function

  DECLARATION:  FSearch(Path : PathStr; Dirlist : String)

      PURPOSE:  Searches for a file in a list of directories

         UNIT:  DOS

  RESULT TYPE:  PathStr

      REMARKS:  This searches for a file defined by Path in the list of
                directories given by DirList.  The directories in DirList.  The
                must be separated by semicolons (;), just as they are in the
                PATH command in DOS.  The search will start in the current
                directory.  The returned value will equal the filename plus
                one of the directory paths, or an empty string if the search
                was unsuccessful.

                The PathStr type is defined in the DOS unit as string[79].