use solid bacgkround for static box as pattern brush can't be properly aligned when it is painted

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@30978 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/statbox.h

@@ -42,6 +42,8 @@ public:
 protected:
     virtual wxSize DoGetBestSize() const;
 
+    virtual WXHBRUSH MSWGetBgBrushForSelf(wxWindow *parent, WXHDC hDC);
+
 private:
     DECLARE_DYNAMIC_CLASS_NO_COPY(wxStaticBox)
 };