Flush() argument should have a default value for compatibility with the other wxConfig versions

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@12444 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/regconf.h

@@ -98,7 +98,7 @@ public:
   bool Write(const wxString& key, bool bValue)
       { return wxConfigBase::Write(key, bValue); }
 
-  virtual bool Flush(bool /* bCurrentOnly = FALSE */ ) { return TRUE; }
+  virtual bool Flush(bool WXUNUSED(bCurrentOnly) = FALSE) { return TRUE; }
 
   // rename
   virtual bool RenameEntry(const wxString& oldName, const wxString& newName);