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/html/m_pre.cpp

@@ -57,7 +57,7 @@ static wxString LINKAGEMODE HtmlizeLinebreaks(const wxString& str)
                     if ( j != end && *j == '\n' )
                         i = j;
                 }
-                // fall through
+                wxFALLTHROUGH;
             case '\n':
                 out << "<br>";
                 break;