Flush procedure

  DECLARATION:  Flush(var F : Text)

      PURPOSE:  Flushes the buffer of a text file open for output

         UNIT:  System

      REMARKS:  F is a text-file variable.  When a text file has been
                opened for output with Append or ReWrite, Flush will empty
                the file's buffer guaranteeing that all characters have, at
                that time, be actually written to the external file.

                NOTES: Has no effect on files open for input.
                       With {$I-}, errors are returned through IOResult