Blender Git Loki

Previewrender (buttons) now supports Lamp, Texture and Sky previews
again. One exception I didn't solve yet... for the Stucci texture.

In a next commit I will add the preview.blend, so people can play with it!

The rules for preview.blend are pretty primitive still... might become
a bit more advanced later. Here's what it uses now:

- If Object has name starting with 'p' it will get the to-be-previewed
Material or Lamp assigned
- If Object has name starting with 't' its Material gets the texture
assigned for Texture previews

The layer codes for current preview options are in DNA_material_types.h;

#define MA_SPHERE 0
#define MA_CUBE 1
#define MA_FLAT 2
#define MA_MONKEY 3
#define MA_SPHERE_A 4
#define MA_TEXTURE 5
#define MA_LAMP 6
#define MA_SKY 7

(SPHERE_A is sphere with alpha for icons)