Add wxTLW::SetModified to allow apps to set the TLW's dirty state. On Mac this gives us the dot in the close button, not implemented elsewhere yet.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62796 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/core/private.h

@@ -753,6 +753,9 @@ public :
 
     static wxNonOwnedWindowImpl* CreateNonOwnedWindow( wxNonOwnedWindow* wxpeer, wxWindow* parent, const wxPoint& pos, const wxSize& size,
     long style, long extraStyle, const wxString& name  ) ;
+    
+    virtual void SetModified(bool WXUNUSED(modified)) { }
+    virtual bool GetModified() const { return false; }
 
 protected :
     wxNonOwnedWindow*   m_wxPeer;