[Fluxus] commits

[Dave Griffiths]

hi all,

* fixed bug in save-primitive for indexed polys as .obj
* added tools for evaluating polygons - these should eventually work on
any type of polygon primitive, they do on most of them now:
  - poly-for-each-face
  - poly-for-each-triangle
  - poly-for-each-tri-sample (random sampling)
* added examples/poly-eval.scm which show how to use these things
* added (rndhemi) and (hrndhemi) for generating points on hemispheres
(solid or hollow)
* added examples/occlusion-bake.scm - should work ok, runs in a thread
for previewing the raytracing

cheers,

dave