Reviewed by Nikolas Zimmermann.

        getBoundingClientRect does not work with SVG <text>
        https://bugs.webkit.org/show_bug.cgi?id=46775

        Dispatched the calls from Element::getBoundingClientRect to getBBox
        through SVGElement::boundingBox.
        Recognized SVGTextElement in addition to SVGStyledLocatableElement
        as a class that provides getBBox.
        Fixed the result of zooming: adjusted the getBoundingClientRect rectangle
        for absolute zoom, even for SVG elements.

        Additional cleanup task:
        Removed redundant overloads of SVGStyledTransformableElement
        methods: nearestViewportElement, farthestViewportElement, getBBox.
        These methods are already inherited from SVGStyledLocatableElement.

        Test: css3/zoom-coords.xhtml

        * WebCore.xcodeproj/project.pbxproj: Set role of SVGLocatable.h to private.
        * dom/Element.cpp:
        (Element::getBoundingClientRect): Used...