Blender Git Loki

- another fresnel improvement. :)
At last irc meeting, eeshlo pointed to an error in the code. It didn't
use the IOR value correctly. This has been solved. So how it works now:
- the IOR button value influences (very subtle) the fresnel effect.
Only for realism diehards.
- the Fresnel value (slider) now denotes the power in the function
rf + (1-rf) * (1-c)^5
where rf= rf = ((ior-1)/(ior+1))^2
and c the dot-product ray/normal.
- so, set the slider at '5' and you have real fresnel. Lower values
for interesting artistic effects.

- put back the forgotten code for gaussian corrected sampling during
antialising render. Normally, each sub-pixel sample in Blender counts
equally, and together make up the pixel color.
With 'Gauss' option set (F10 menu) each sub-pixel sample creates a small
weighted mask with variable size, which (can) affect neighbouring pixels
as well. The result is smoother edges, less sensitive for gamma, and
well suited to reduce motion-aliasing (when things move extreme slow).
This is result of *long* period of research in NeoGeo days, and based on
every scientific sampling/reconstructing theory we could find. Plus a
little bit of our selves. :)

- I should write once how blender constructs Jitter tables for sub-sampling.
this is a very nice method, and superior to normal block filter or random
jittering... time!