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/sashtest/sashtest.cpp

@@ -28,7 +28,7 @@
 MyFrame *frame = NULL;
 wxList my_children;
 
-IMPLEMENT_APP(MyApp)
+wxIMPLEMENT_APP(MyApp);
 
 // For drawing lines in a canvas
 long xpos = -1;