Cycles / Wireframe node:

* Added a wireframe node (Input category) to get access to Mesh wireframe data. 
The thickness can be controlled via a "Size" parameter, and is available in world units (default) and screen pixel size. 
* Only the triangulated mesh is available now, quads is for later. 

Documentation:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes/More#Wireframe

Render and Example file:
http://www.pasteall.org/pic/show.php?id=51731
http://www.pasteall.org/blend/21510

intern/cycles/render/nodes.h

@@ -442,6 +442,13 @@ public:
 	SHADER_NODE_CLASS(LayerWeightNode)
 };
 
+class WireframeNode : public ShaderNode {
+public:
+	SHADER_NODE_CLASS(WireframeNode)
+	
+	bool use_pixel_size;
+};
+
 class MathNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(MathNode)