Cycles: Ashikhmin-Shirley anisotropic BSDF

* Ashikhmin-Shirley anisotropic BSDF was added as closure
* Anisotropic BSDF node now has two distributions

Reviewers: brecht, dingto

Differential Revision: https://developer.blender.org/D549

intern/cycles/render/nodes.h

@@ -218,9 +218,13 @@ public:
 	bool scattering;
 };
 
-class WardBsdfNode : public BsdfNode {
+class AnisotropicBsdfNode : public BsdfNode {
 public:
-	SHADER_NODE_CLASS(WardBsdfNode)
+	SHADER_NODE_CLASS(AnisotropicBsdfNode)
+
+	ustring distribution;
+	static ShaderEnum distribution_enum;
+
 	void attributes(Shader *shader, AttributeRequestSet *attributes);
 };