Use wx-prefixed macros throughout the repository.

Change {DECLARE,IMPLEMENT}_*CLASS and {DECLARE,BEGIN,END}_EVENT_TABLE
occurrences to use the wx-prefixed version of the macros.

samples/html/helpview/helpview.cpp

@@ -54,7 +54,7 @@ private:
 };
 
 
-IMPLEMENT_APP(MyApp)
+wxIMPLEMENT_APP(MyApp);
 
 
 bool MyApp::OnInit()