SONOpenOldFile

  SONOPENOLDFILE opens an existing a SON file and returns a handle
  from SON32.DLL. Note that this is not a MATLAB handle.
  FH=SONOPENOLDFILE(filename, iMode)
                      filename is a string
                      iMode = 0 for Read/Write
                              1 for Read Only
                              2 for Read/Write but accept Read Only

  Returns the SON file handle or a negative error code

  Author:Malcolm Lidierth
  Matlab SON library:
  Copyright © The Author & King's College London 2005-2006