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/spinctlg.cpp

@@ -680,7 +680,7 @@ wxString wxSpinCtrl::DoValueToText(double val)
 
         default:
             wxFAIL_MSG( wxS("Unsupported spin control base") );
-            // Fall through
+            wxFALLTHROUGH;
 
         case 10:
             return wxString::Format("%ld", static_cast<long>(val));