How to add a new node to the Cycles source code

I created a page where I documented each file that needed to be changed or added to create the VoronoiCrackle node that I would like to get included in Blender. It documents what is what and contains a link to the actual patch. It is certainly not perfect but might serve as a good starting point for people how want to give it a try (and for myself as a cheat sheet because adding a node involves many, many files :-)
The page is listed in the pages widget on the top right of the blog or via this link.