Some webkit version doesn't implement classList for SVGElement but only for HTMLElement. Add condition to check that.

Hi,
The first condition was "if classList exists on createElement", but it would be useful to check it for SVG too.
Old Webkit versions implement classList for HTMLElement but not for SVGElement. This is fixed in last releases. See https://bugs.webkit.org/show_bug.cgi?id=74959
That was annoying because PhantomJS 1.9.2 + QUnit on a SVG library can be annoying.

Have a nice day :)