Add wxTopLevelWindow::Enable{Maximize,Minimize}Button()

Allow to disable maximize and minimize buttons dynamically just as we already
allow to disable the "Close" button using EnableCloseButton().

Currently implemented for MSW and OSX only.

Closes #17133.

include/wx/osx/core/private.h

@@ -848,6 +848,8 @@ public :
     virtual void SetTitle( const wxString& title, wxFontEncoding encoding ) = 0;
 
     virtual bool EnableCloseButton(bool enable) = 0;
+    virtual bool EnableMaximizeButton(bool enable) = 0;
+    virtual bool EnableMinimizeButton(bool enable) = 0;
 
     virtual bool IsMaximized() const = 0;