Introduce skeleton of taskbar button feature.

- Add classes: wxTaskBarButton and wxTaskBarButtonImpl.
- New interface in wxTopLevelWindowMSW to get its wxTaskBarButton:
    MSWGetTaskBarButton.
- A simple sample and build files under msvc.

Author: Chaobin Zhang

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77591 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/taskbarbutton.h

@@ -0,0 +1,35 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        include/wx/msw/taskbarbutton.h
+// Purpose:     Defines wxTaskBarButtonImpl class.
+// Author:      Chaobin Zhang <zhchbin@gmail.com>
+// Created:     2014-06-01
+// Copyright:   (c) 2014 wxWidgets development team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#ifndef  _WX_MSW_TASKBARBUTTON_H_
+#define  _WX_MSW_TASKBARBUTTON_H_
+
+#if wxUSE_TASKBARBUTTON
+
+#include "wx/defs.h"
+
+struct ITaskbarList3;
+
+class wxTaskBarButtonImpl : public wxTaskBarButton {
+public:
+    virtual ~wxTaskBarButtonImpl();
+
+    virtual void SetProgressValue(int value) wxOVERRIDE;
+
+private:
+    friend class wxTopLevelWindowMSW;
+    wxTaskBarButtonImpl(WXWidget parent);
+
+    WXWidget m_hwnd;
+    ITaskbarList3 *m_taskbarList;
+};
+
+#endif // wxUSE_TASKBARBUTTON
+
+#endif  // _WX_MSW_TASKBARBUTTON_H_