generate middle click events (backport from HEAD of the patch 1521314)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43585 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

wxPython/demo/Main.py

@@ -1772,8 +1772,9 @@ class MySplashScreen(wx.SplashScreen):
         if self.fc.IsRunning():
             self.Raise()
         
+import wx.lib.mixins.inspect
 
-class MyApp(wx.App):
+class MyApp(wx.App, wx.lib.mixins.inspect.InspectionMixin):
     def OnInit(self):
         """
         Create and show the splash screen.  It will then create and show
@@ -1794,6 +1795,9 @@ class MyApp(wx.App):
         splash = MySplashScreen()
         splash.Show()
 
+        # Setup the InspectionMixin
+        self.Init()
+        
         return True