Split Normals I (5/5): Add support of split normals to Cycles.

Idea and code by Brecht, many thanks!

Reviewers: brecht

Reviewed By: brecht

CC: campbellbarton, dingto

Differential Revision: https://developer.blender.org/D369

intern/cycles/render/mesh.h

@@ -114,6 +114,7 @@ public:
 	void add_triangle(int v0, int v1, int v2, int shader, bool smooth);
 	void add_curve_key(float3 loc, float radius);
 	void add_curve(int first_key, int num_keys, int shader);
+	int split_vertex(int vertex);
 
 	void compute_bounds();
 	void add_face_normals();