fix($location): parse xlink:href for SVGAElements

Before this fix, the xlink:href property of an SVG `<a>` element could not be parsed on click, as the property is an SVGAnimatedString rather than a DOMString.

This patch parses the xlink:href's animVal into a DOMString in order to prevent an `Object #<SVGAnimatedString> has no method 'indexOf'` exception from being thrown, and also to update the location if necessary as expected.

Fixes #5198, #5199, #4098, #1420