gtk/widget.go
func (v *Widget) SetMarginTop(margin int) {
	C.gtk_widget_set_margin_top(v.native(), C.gint(margin))
}
func (v *Widget) SetMarginTop(margin int) {
	C.gtk_widget_set_margin_top(v.native(), C.gint(margin))
}
// SetMarginTop is a wrapper around gtk_widget_set_margin_top().