Allow using custom labels for wxGenericMessageDialog buttons.

Custom labels set for wxGenericMessageDialog buttons were simply ignored as it
used CreateSeparatedButtonSizer() to create the actual buttons which in turn
always used the standard labels.

Fix this by explicitly creating the buttons with custom labels if necessary.

This also fixes custom label support in wxGenericRichMessageDialog deriving
from this class.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65449 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/msgdlgg.h

@@ -12,6 +12,8 @@
 #ifndef _WX_GENERIC_MSGDLGG_H_
 #define _WX_GENERIC_MSGDLGG_H_
 
+class WXDLLIMPEXP_FWD_CORE wxSizer;
+
 class WXDLLIMPEXP_CORE wxGenericMessageDialog : public wxMessageDialogBase
 {
 public:
@@ -37,6 +39,12 @@ protected:
     virtual void AddMessageDialogDetails(wxSizer *WXUNUSED(sizer)) { }
 
 private:
+    // Creates and returns a standard button sizer using the style of this
+    // dialog and the custom labels, if any.
+    //
+    // May return NULL on smart phone platforms not using buttons at all.
+    wxSizer *CreateMsgDlgButtonSizer();
+
     wxPoint m_pos;
     bool m_created;