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/taskbarbutton.h

@@ -0,0 +1,40 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        include/taskbarbutton.h
+// Purpose:     Defines wxTaskBarButton class for manipulating buttons on the
+//              windows taskbar.
+// Author:      Chaobin Zhang <zhchbin@gmail.com>
+// Created:     2014-04-30
+// Copyright:   (c) 2014 wxWidgets development team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_TASKBARBUTTON_H_
+#define _WX_TASKBARBUTTON_H_
+
+#if wxUSE_TASKBARBUTTON
+
+// ----------------------------------------------------------------------------
+// wxTaskBarButton: define wxTaskBarButton interface.
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_ADV wxTaskBarButton
+{
+public:
+    wxTaskBarButton() { }
+    virtual ~wxTaskBarButton() { }
+
+    // Operations:
+    virtual void SetProgressValue(int value) = 0;
+
+private:
+    wxDECLARE_NO_COPY_CLASS(wxTaskBarButton);
+};
+
+
+#if defined(__WXMSW__)
+    #include "wx/msw/taskbarbutton.h"
+#endif
+
+#endif // wxUSE_TASKBARBUTTON
+
+#endif  // _WX_TASKBARBUTTON_H_