Snow regeneration

[xoft]

Nice. I like the patch, I'll just take the liberty of pushing the "snowing code" to a separate function, out of cChunk::Tick().
Also, I'm not so sure about the naming, "nice" is subjective, someone might find that kind of snow terrible. How about calling it "snowdrift" or "highsnow" in the ini file?

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or "deepsnow", that might be the most accurate and pronounces well