process one event at once in wxEvtHandler::ProcessPendingEvents() to prevent crashes when a (pending) event handler destroys the event handler object itself; only add the event handler to wxPendingEvents list if it's not already there (and explicitly mention that an object can be present in this list only once in the comment) (replaces patch 1837719)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51021 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/event.h

@@ -3008,8 +3008,9 @@ typedef void (wxEvtHandler::*wxClipboardTextEventFunction)(wxClipboardTextEvent&
 // Global data
 // ----------------------------------------------------------------------------
 
-// for pending event processing - notice that there is intentionally no
-// WXDLLEXPORT here
+// list containing event handlers with pending events for them
+//
+// notice that each event handler should occur at most once in this list
 extern WXDLLIMPEXP_BASE wxList *wxPendingEvents;
 #if wxUSE_THREADS
     extern WXDLLIMPEXP_BASE wxCriticalSection *wxPendingEventsLocker;