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/printing/printing.h

@@ -33,7 +33,7 @@ private:
     wxFont    m_testFont;
 };
 
-DECLARE_APP(MyApp)
+wxDECLARE_APP(MyApp);
 class MyCanvas;
 
 // Define a new canvas and frame