Add wxWindow::ProcessWindowEventLocally() and use it in wxMSW MDI code.

Add ProcessWindowEventLocally() which wraps ProcessEventLocally() in the same
way as ProcessWindowEvent() wraps ProcessEvent(). I.e. it allows to process
the event in this window only, without propagating it upwards, but taking into
account any event handlers associated with it.

Use the new method in wxMDIParentFrame code in wxMSW to ensure that event
handlers pushed on MDI children frames are taken into account. Add a test for
this to the MDI sample.

Closes #11225.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64262 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/window.h

@@ -1840,6 +1840,19 @@ public:
     */
     bool ProcessWindowEvent(wxEvent& event);
 
+    /**
+        Wrapper for wxEvtHandler::ProcessEventLocally().
+
+        This method is similar to ProcessWindowEvent() but can be used to
+        search for the event handler only in this window and any event handlers
+        pushed on top of it. Unlike ProcessWindowEvent() it won't propagate the
+        event upwards. But unlike wxEvtHandler::ProcessEventHere() it will use
+        the event handlers associated with this window.
+
+        @since 2.9.1
+     */
+    bool ProcessWindowEventLocally(wxEvent& event);
+
     /**
         Removes and returns the top-most event handler on the event handler stack.