Cycles: per-BSDF normal input and new Bump node.

Each BSDF node now has a Normal input, which can be used to set a custom normal
for the BSDF, for example if you want to have only bump on one of the layers in
a multilayer material.

The Bump node can be used to generate a normal from a scalar value, the same as
what happens when you connect a scalar value to the displacement output.

Documentation has been updated with the latest changes:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes

Patch by Agustin Benavidez, some implementation tweaks by me.

intern/cycles/render/nodes.h

@@ -440,6 +440,11 @@ public:
 	float4 ramp[RAMP_TABLE_SIZE];
 };
 
+class SetNormalNode : public ShaderNode {
+public:
+	SHADER_NODE_CLASS(SetNormalNode)
+};
+
 CCL_NAMESPACE_END
 
 #endif /* __NODES_H__ */