Refresh wxMSW wxStaticBitmap when its size changes.

As MSW native control centers the image, it must be entirely redrawn when the
area in which the image is centered changes, but it doesn't happen by default,
so do it ourselves explicitly.

Also explain that this centering behaviour is platform-specific and shouldn't
be relied upon.

Closes #4564.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73485 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/statbmp.h

@@ -76,6 +76,7 @@ protected:
     void DoPaintManually(wxPaintEvent& event);
 #endif // !__WXWINCE__
 
+    void WXHandleSize(wxSizeEvent& event);
 
     // we can have either an icon or a bitmap
     bool m_isIcon;
@@ -86,6 +87,7 @@ protected:
 
 private:
     DECLARE_DYNAMIC_CLASS(wxStaticBitmap)
+    wxDECLARE_EVENT_TABLE();
     wxDECLARE_NO_COPY_CLASS(wxStaticBitmap);
 };