SVGHMI: provide request_animate() to Widget authors so that they can register redraw code when events lead to redraw. Widget member animate() is called when it is time to update DOM.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
  <TargetType>
    <Linux/>
  </TargetType>
</BeremizRoot>