Implement wxWindow::ShowWithEffect() for wxOSX/Cocoa.

This version animates the window asynchronously and is being checked in just
to preserve it in svn if we later decide to return to this semantics. It will
be replaced by synchronous animation in the next commit.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62304 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/cocoa/private.h

@@ -73,6 +73,17 @@ public :
     virtual bool        IsVisible() const ;
     virtual void        SetVisibility(bool);
 
+    // we provide a static function which can be reused from
+    // wxNonOwnedWindowCocoaImpl too
+    static bool ShowViewOrWindowWithEffect(wxWindow *win,
+                                           bool show,
+                                           wxShowEffect effect,
+                                           unsigned timeout);
+
+    virtual bool ShowWithEffect(bool show,
+                                wxShowEffect effect,
+                                unsigned timeout);
+
     virtual void        Raise();
 
     virtual void        Lower();
@@ -190,7 +201,10 @@ public :
     void Raise();
     void Lower();
     bool Show(bool show);
-    bool ShowWithEffect(bool show, wxShowEffect effect, unsigned timeout);
+
+    virtual bool ShowWithEffect(bool show,
+                                wxShowEffect effect,
+                                unsigned timeout);
 
     void Update();
     bool SetTransparent(wxByte alpha);