Provide a task-dialog based wxMSW wxMessageDialog implementation.

Use the task dialog instead of the legacy message box for wxMessageDialog
implementation under wxMSW on recent (Vista and later) Windows versions.

As part of this change, remove wxMessageDialogWithCustomLabels and integrate
its functionality in wxMessageDialogBase itself as it's now used by all
platforms.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65348 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/msgdlg.h

@@ -12,7 +12,7 @@
 #ifndef _WX_MSGBOXDLG_H_
 #define _WX_MSGBOXDLG_H_
 
-class WXDLLIMPEXP_CORE wxMessageDialog : public wxMessageDialogWithCustomLabels
+class WXDLLIMPEXP_CORE wxMessageDialog : public wxMessageDialogBase
 {
 public:
     wxMessageDialog(wxWindow *parent,
@@ -20,7 +20,7 @@ public:
                     const wxString& caption = wxMessageBoxCaptionStr,
                     long style = wxOK|wxCENTRE,
                     const wxPoint& WXUNUSED(pos) = wxDefaultPosition)
-        : wxMessageDialogWithCustomLabels(parent, message, caption, style)
+        : wxMessageDialogBase(parent, message, caption, style)
     {
         m_hook = NULL;
     }
@@ -55,11 +55,16 @@ private:
     // offset all buttons starting from the first one given by dx to the right
     void OffsetButtonsStartingFrom(int first, int dx);
 
+    // used by ShowModal() to display a message box when task dialogs
+    // aren't available.
+    int ShowMessageBox();
+
+    // used by ShowModal() to display a task dialog.
+    int ShowTaskDialog();
 
     WXHANDLE m_hook; // HHOOK used to position the message box
 
-    DECLARE_DYNAMIC_CLASS(wxMessageDialog)
-    wxDECLARE_NO_COPY_CLASS(wxMessageDialog);
+    wxDECLARE_DYNAMIC_CLASS_NO_COPY(wxMessageDialog);
 };