Add wxTopLevelWindow::SetRepresentedFilename().

This currently is only implemented under OS X and sets the proxy icon there
but could be implemented to do something useful under the other platforms too
in the future.

Closes #13797.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70295 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/core/private.h

@@ -863,6 +863,8 @@ public :
     virtual void SetModified(bool WXUNUSED(modified)) { }
     virtual bool IsModified() const { return false; }
 
+    virtual void SetRepresentedFilename(const wxString& WXUNUSED(filename)) { }
+
 #if wxOSX_USE_IPHONE
     virtual CGFloat GetWindowLevel() const { return 0.0; }
 #else