adding wxFALLTHROUGH where until now we had comments, allows for code-analysis support

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76399 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/calctrlg.cpp

@@ -1378,7 +1378,7 @@ void wxGenericCalendarCtrl::OnClick(wxMouseEvent& event)
 
         default:
             wxFAIL_MSG(wxT("unknown hittest code"));
-            // fall through
+            wxFALLTHROUGH;
 
         case wxCAL_HITTEST_NOWHERE:
             event.Skip();