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/cocoa/private.h

@@ -239,6 +239,8 @@ public :
     virtual void SetModified(bool modified);
     virtual bool IsModified() const;
 
+    virtual void SetRepresentedFilename(const wxString& filename);
+
     wxNonOwnedWindow*   GetWXPeer() { return m_wxPeer; }
     
     CGWindowLevel   GetWindowLevel() const { return m_macWindowLevel; }