Add a ton of code to render a couple new textures to other textures, to be used later when actually rendering tree bits (leaves -- though that'll require a lot *more* code -- bark and foliage.  Add sizes to all texture objects after they load.  Add a barrier callback to initTextures that sets up the tree data when enough textures have finished.  Add new shaders used for rendering to the texture.
Add (unused) vine texture to the list returned by initTextures