Blender Git Loki

Displacement map

- changed code to make use of actual textures, not the hackish
'externtex', which is only for tools
- added a 'displacement' vector in ShadeInput, and moved calculation of
displacement vector to texture.c itself. So it works with stencil, but
also for options as 'add', 'mult' and 'sub'.
- for RGB textures it uses the brightness value of color for displace
- for stucci, and plugin textures returning a normal, it uses that

- Also: wrote call in end of preparing renderfaces, to split non-flat
quad faces in triangles. gives a lot fewer errors in displace textures,
but also raytracing irregular subsurfs goes better now.

- texture mapping that works for displace: orco, sticky, global, obj, normal.
UV not yet. Reflection-displace? uhh! :)