Blender Git Loki

Orange; daily noodler update commit.

- Adding execution code for Node trees. Was a bit a puzzle, since I want
it to be multithreading by design. This now is solved by defining a
stack per tree for all data that's being written into. This stack, which
resides now in the NodeTree itself, then can be allocated per thread.

- For testing pleasure, I've added a 'mix node' and a 'show node', so
you can already see it do something. :)

- reshuffled structure, to put things nice together, and have easier node
adding. Current state is still WIP though, structure might change.
For the record; new file node_shaders.c will contain all shader node
definitions, apart from the drawing callbacks.

Next: I'm going to check on Andrea's work on icons now, since this is very
much needed for true shader/composit work.
Now back to release work...