Cycles / Blackbody node:

* Replaced the Brute Force version with a nice lookup table, this speeds it up a lot. 
Patch by Philipp Oeser (lichtwerk) with some cleanup and changes by myself. Thanks! 

ToDo:
* Temperature values between 800 and 804 Kelvin are wrong in SVM, check on this.

intern/cycles/render/nodes.h

@@ -465,6 +465,8 @@ public:
 class BlackbodyNode : public ShaderNode {
 public:
 	SHADER_NODE_CLASS(BlackbodyNode)
+	
+	bool has_converter_blackbody() { return true; }
 };
 
 class MathNode : public ShaderNode {