Cycles: Add dedicated nodes to split/combine vectors.

This was already possible via the RGB nodes, but that seems weird.

intern/cycles/kernel/shaders/node_separate_xyz.osl

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2011-2013 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+#include "stdosl.h"
+
+shader node_separate_xyz(
+	vector Vector = 0.8,
+	output float X = 0.0,
+	output float Y = 0.0,
+	output float Z = 0.0)
+{
+	X = Vector[0];
+	Y = Vector[1];
+	Z = Vector[2];
+}