It is now dual-licensed BSD-3-Clause and GPL-2.0, we use the former. The PATENTS file is no longer applicable \o/ Also add zstd to COPYRIGHT.txt
Following upstream commit f04deff4fc
zstd has much better compression speed and ratio, and better decompression speed than currently available methods. Also set zstd as the default compression method for Compression as well as FileAccessCompressed functions.
