Generate the button clicks in GTK version of wxInfoBar.

Also add an example of handling info bar buttons events to the sample and
mention that this must be done using Connect() or by deriving from wxInfoBar
in the documentation.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62279 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/dialogs/dialogs.h

@@ -429,6 +429,8 @@ private:
     wxWindow *m_canvas;
 
 #if wxUSE_INFOBAR
+    void OnInfoBarRedo(wxCommandEvent& event);
+
     wxInfoBar *m_infoBarSimple,
               *m_infoBarAdvanced;
 #endif // wxUSE_INFOBAR