Add wxRichMessageDialog class.

This is a generalization of wxMessageDialog based on the native task dialog
under recent (Vista and later) Windows versions and implemented generically
for the other ports for now.

It provides the possibility to use additional controls in the message boxes
(checkbox useful for the "Don't ask me again" kind of dialogs and collapsible
detailed explanations field) and better look and feel under Windows.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65349 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/richmsgdlg.h

@@ -0,0 +1,31 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        wx/msw/richmsgdlg.h
+// Purpose:     wxRichMessageDialog
+// Author:      Rickard Westerlund
+// Created:     2010-07-04
+// RCS-ID:      $Id$
+// Copyright:   (c) 2010 wxWidgets team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_MSW_RICHMSGDLG_H_
+#define _WX_MSW_RICHMSGDLG_H_
+
+class WXDLLIMPEXP_CORE wxRichMessageDialog : public wxGenericRichMessageDialog
+{
+public:
+    wxRichMessageDialog(wxWindow *parent,
+                        const wxString& message,
+                        const wxString& caption,
+                        long style)
+        : wxGenericRichMessageDialog(parent, message, caption, style)
+        { }
+
+    // overridden base class method showing the native task dialog if possible
+    virtual int ShowModal();
+
+private:
+    wxDECLARE_DYNAMIC_CLASS_NO_COPY(wxRichMessageDialog);
+};
+
+#endif // _WX_MSW_RICHMSGDLG_H_