Blender Git Loki

Interesting commit for artists using huge textures;

The code that generated mipmaps took a real long time to do it... on a
5k x 5k image it took here (no optim, debug compile) 32.5 sec.

Recoded the very old filtering routine, which already brought it down to
2.8 seconds. Then tested if we even need this filtering... in many cases
the images are painted or photographs, which is filtered OK already.
Without the filter, the mipmap timing went down to 0.39 second. :)

http://www.blender.org/bf/filters/index1.html

Here's an example of two 'mips' generated with or without gauss filter.
Note that aliasing in an image remains there... which can be a wanted
effect anyway.

So; added the gauss filter as option in making mipmaps. Also had to
reshuffle the buttons there in a more logical manner.
There's also disabled code in the do_versions to set 'gauss' on in older
files. Will be enabled during release time.