This is now a "mix" between the original and the alternate drawing
strategy, hopefully combining its strength. In detail:
1. Intensity of light sources aren't added together anymore. Instead,
the brightest light source decides end brightness pre-smoothing.
2. For smoothing, we update normals more quickly than brightness. This is
the main change relative to the first "alternate" version. Actually
quite embarassing that I didn't think of this solution before %)
This is still a tad busier than what we have currently, simply due to
normals changing around more quickly. On the plus side, Clonk faces
shouldn't go dark anymore while walking, so that's something.
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