784 - Fix clip-path with base element on the same page

This commit adds the current document's URL to the clip-path URL so `<base>` elements do not break the URL (assuming `<base href="/">` and `clip-path="url(#clipPath1)"` the URL `#clipPath1` becomes `/#clipPath1` which obviously won't work).

Close #784.

This new PR includes a browser switch that only applies the fix on non-IE≤9-browsers, because those browsers do not respect the base element in SVG context.