Stop using wxBU_AUTODRAW in wxWidgets code

This style bit is obsolete and doesn't do anything, so remove confusing
references to it.

interface/wx/cshelp.h

@@ -271,7 +271,7 @@ public:
                         wxWindowID id = wxID_CONTEXT_HELP,
                         const wxPoint& pos = wxDefaultPosition,
                         const wxSize& size = wxDefaultSize,
-                        long style = wxBU_AUTODRAW);
+                        long style = 0);
 };