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/common/textfile.cpp

@@ -64,7 +64,7 @@ bool wxTextFile::OnOpen(const wxString &strBufferName, wxTextBufferOpenMode Open
     {
         default:
             wxFAIL_MSG( wxT("unknown open mode in wxTextFile::Open") );
-            // fall through
+            wxFALLTHROUGH;
 
         case ReadAccess :
             FileOpenMode = wxFile::read;