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/xrc/xrcdemo.cpp

@@ -59,7 +59,7 @@
 // static object for many reasons) and also declares the accessor function
 // wxGetApp() which will return the reference of the right type (i.e. the_app and
 // not wxApp).
-IMPLEMENT_APP(MyApp)
+wxIMPLEMENT_APP(MyApp);
 
 //-----------------------------------------------------------------------------
 // Public methods