Cycles / Wavelength to RGB node:

* Added a node to convert wavelength (in nanometer, from 380nm to 780nm) to RGB values. This can be useful to match real world colors easier.

Example render:
http://www.pasteall.org/pic/show.php?id=53202

ToDo:
* Move some functions into an util file, maybe a common util_color.h or so.
* Test GPU, unfortunately sm_21 doesn't work for me yet.

source/blender/blenkernel/intern/node.c

@@ -3399,6 +3399,7 @@ static void registerShaderNodes(void)
 	register_node_type_sh_value();
 	register_node_type_sh_rgb();
 	register_node_type_sh_wireframe();
+	register_node_type_sh_wavelength();
 	register_node_type_sh_mix_rgb();
 	register_node_type_sh_valtorgb();
 	register_node_type_sh_rgbtobw();