fixed mouse input handling in wxUniv: the static boxes ust be transparent

or the windows inside them don't get any mouse events at all


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@14318 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/univ/statbox.h

@@ -58,6 +58,10 @@ protected:
     // get the size of the border
     wxRect GetBorderGeometry() const;
 
+    // returning TRUE from here ensures that we act as a container window for
+    // our children
+    virtual bool IsStaticBox() const { return TRUE; }
+
 private:
     DECLARE_DYNAMIC_CLASS(wxStaticBox)
 };