infinite loop with patterns on ctx.fill();

[murkle]

Minimal test case (hangs browser on "ctx.fill();")
http://test.geogebra.org/~mike/canvas2svgPatternBug/imageFill.html

Proof of concept for suggested fix:
http://test.geogebra.org/~mike/canvas2svgPatternBug/imageFill_fixed.html

Changing

while(value.__ctx.__defs.childNodes.length) {
id = value.__ctx.__defs.childNodes[0].getAttribute("id");
this.__ids[id] = id;
this.__defs.appendChild(value.__ctx.__defs.childNodes[0]);
}

to

var len = value.__ctx.__defs.childNodes.length;
for (var i = 0 ; i < len ; i++) {
id = value.__ctx.__defs.childNodes[i].getAttribute("id");
this.__ids[id] = id;
this.__defs.appendChild(value.__ctx.__defs.childNodes[i]);
}

seems to fix it although maybe removing the elements would be better (I guess there's a line of code missing to do that)

[murkle]

Same as #49