This completes the pipeline make-over, as started in 2006. With this
option, during rendering, each sample for every layer and pass is being
saved on disk (looks like non-antialiased images). Then the composite
and color correction happens, then a clip to 0-1 range, and only in end
all samples get combined - using sampling filters such as gauss/mitch/catmul.
This results in artefact-free antialiased images. Even Z-combine or
ID masks now work perfect for it!
This is an unfinished commit btw; Brecht will finish this for strands.
Also Halo doesnt work yet.
To activate FSA: press "Save Buffers" and the new button next to it. :)