Fixed possible ClassCastException that was caused by my earlier attempt to support...

Fixed possible ClassCastException that was caused by my earlier attempt to support SVG 1.2. Batik's SAXSVGDocumentFactory doesn't currently deal well with the case when namespaces are declared outside of its scope. Worked around that by doing the SVG version detection in FOP code. SVG12DOMImplementation is obtained by reflection in order to keep backwards compatilibility with earlier Batik versions that don't support SVG 1.2.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@719646 13f79535-47bb-0310-9956-ffa450edef68