message: Simplify check for restricted filename characters
  Eliminates use of C-style cast.
diff: @@ -153,25 +153,11 @@ void FileIo::fileNameModified(Control* control)
  {
  std::string sFile = control->text();
  + const std::string RestrictedFilenameChars = "\\/:*?\"<>|";
  +
  if (sFile.empty()) // no blank filename
  btnFileOp.enabled(false);
  - else if ((int)sFile.find('\\')>-1) // no \ in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find('/')>-1) // no / in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find(':')>-1) // no : in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find('*')>-1) // no * in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find('?')>-1) // no ? in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find('"')>-1) // no " in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find('<')>-1) // no < in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find('>')>-1) // no > in the filename
  - btnFileOp.enabled(false);
  - else if ((int)sFile.find('|')>-1) // no | in the filename
  + else if (sFile.find_first_of(RestrictedFilenameChars) != std::string::npos)
  btnFileOp.enabled(false);
  else
  btnFileOp.enabled(true);
  