fixed bug with inverted ClippingNode with DrawNode as stencil on Canvas;

_Summary:_
_setInverted(true)_ doesn't work if You're using _DrawNode_ as _stencil_ on _canvas_ renderer;

_Reproduce steps:_
-Set _renderMode_ to _canvas_
-Add _ClippingNode_
-Set _inverted_ to _true_ for _ClippingNode_
-Set _DrawNode_ as stencil;
Expected results:
everything draws outside DrawNode;
Actual results:
everything is drawn inside DrawNode;

For quick reproduce:
-set renderMode
-add these lines at the end of _MyLayer.init_ function in template

---
        for (var i = 0; i < 2; ++i) {
            var s = cc.size(size.width, size.height / 2);
            var white = cc.color(255, 255, 255, 255);

            var node = cc.ClippingNode.create();

            var fadeLayer = cc.LayerColor.create(white, s.width, s.height);
            node.addChild(fadeLayer);

            var stencil = cc.DrawNode.create();
            var rectangle = [
                cc.p(s.width * 0.25, s.height * 0.25),
                cc.p(s.width * 0.25, s.height * 0.75),
                cc.p(s.width * 0.75, s.height * 0.75),
                cc.p(s.width * 0.75, s.height * 0.25)
            ];
            stencil.drawPoly(rectangle, white, 1, white);
            node.setInverted(i % 2);
            node.setStencil(stencil);

            node.setPosition(0, (i % 2) * size.height / 2);
            this.addChild(node);
        }
---

There's a restriction in this solution: only clockwise polygons are supported;

before:
![before](https://cloud.githubusercontent.com/assets/4687396/3172771/8aaff178-ebda-11e3-82f9-02d1438bd751.png)
after:
![after](https://cloud.githubusercontent.com/assets/4687396/3172773/8e3d31ac-ebda-11e3-9c58-ecec7736cb7d.png)