send destroy events for children before they're fully destroyed; document SendDestroyEvent() and explain when to call it

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58252 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/window.h

@@ -2815,6 +2815,15 @@ protected:
         @deprecated @todo provide deprecation description
     */
     virtual void SetInitialBestSize(const wxSize& size);
+
+    /**
+        Generate wxWindowDestroyEvent for this window.
+
+        This is called by the window itself when it is being destroyed and
+        usually there is no need to call it but see wxWindowDestroyEvent for
+        explanations of when you might want to do it.
+     */
+    void SendDestroyEvent();
 };