Zstd

perf: better decompression speed on large files (+7%) and cold dictionaries (+15%)
perf: slightly better compression ratio at high compression modes
api : finalized advanced API, last stage before "stable" status
api : new --rsyncable mode, by terrelln
api : support decompression of empty frames into NULL (used to be an error) (1385)
build: new set of macros to build a minimal size decoder, by felixhandte
build: fix compilation on MIPS32, reported by clbr (1441)
build: fix compilation with multiple -arch flags, by ryandesign
build: highly upgraded meson build, by lzutao
build: improved buck support, by obelisk
build: fix cmake script : can create debug build, by pitrou
build: Makefile : grep works on both colored consoles and systems without color support
build: fixed zstd-pgo, by bmwiedemann
cli : support ZSTD_CLEVEL environment variable, by yijinfb (1423)
cli : --no-progress flag, preserving final summary (1371), by terrelln
cli : ensure destination file is not source file (1422)
cli : clearer error messages, especially when input file not present
doc : clarified zstd_compression_format.md, by ulikunitz
misc: fixed zstdgrep, returns 1 on failure, by lzutao
misc: NEWS renamed as CHANGELOG, in accordance with fboss

perf: slightly better decompression speed on clang (depending on hardware target)
fix : performance of dictionary compression for small input < 4 KB at levels 9 and 10
build: no longer build backtrace by default in release mode; restrict further automatic mode
build: control backtrace support through build macro BACKTRACE
misc: added man pages for zstdless and zstdgrep, by samrussell

perf: much faster dictionary builder, by jenniferliu
perf: faster dictionary compression on small data when using multiple contexts, by felixhandte
perf: faster dictionary decompression when using a very large number of dictionaries simultaneously
cli : fix : does no longer overwrite destination when source does not exist (1082)
cli : new command --adapt, for automatic compression level adaptation
api : fix : block api can be streamed with > 4 GB, reported by catid
api : reduced ZSTD_DDict size by 2 KB
api : minimum negative compression level is defined, and can be queried using ZSTD_minCLevel().
build: support Haiku target, by korli
build: Read Legacy format is limited to v0.5+ by default. Can be changed at compile time with macro ZSTD_LEGACY_SUPPORT.
doc : zstd_compression_format.md updated to match wording in IETF RFC 8478
misc: tests/paramgrill, a parameter optimizer, by GeorgeLu97

perf: much faster dictionary compression, by felixhandte
perf: small quality improvement for dictionary generation, by terrelln
perf: slightly improved high compression levels (notably level 19)
mem : automatic memory release for long duration contexts
cli : fix : overlapLog can be manually set
cli : fix : decoding invalid lz4 frames
api : fix : performance degradation for dictionary compression when using advanced API, by terrelln
api : change : clarify ZSTD_CCtx_reset() vs ZSTD_CCtx_resetParameters(), by terrelln
build: select custom libzstd scope through control macros, by GeorgeLu97
build: OpenBSD patch, by bket
build: make and make all are compatible with -j
doc : clarify zstd_compression_format.md, updated for IETF RFC process
misc: pzstd compatible with reproducible compilation, by lamby

perf: faster speed (especially decoding speed) on recent cpus (haswell+)
perf: much better performance associating --long with multi-threading, by terrelln
perf: better compression at levels 13-15
cli : asynchronous compression by default, for faster experience (use --single-thread for former behavior)
cli : smoother status report in multi-threading mode
cli : added command --fast=, for faster compression modes
cli : fix crash when not overwriting existing files, by Pádraig Brady (pixelb)
api : `nbThreads` becomes `nbWorkers` : 1 triggers asynchronous mode
api : compression levels can be negative, for even more speed
api : ZSTD_getFrameProgression() : get precise progress status of ZSTDMT anytime
api : ZSTDMT can accept new compression parameters during compression
api : implemented all advanced dictionary decompression prototypes
build: improved meson recipe, by Shawn Landden (shawnl)
build: VS2017 scripts, by HaydnTrigg
misc: all /contrib projects fixed
misc: added /contrib/docker script by gyscos

perf: faster zstd_opt strategy (levels 16-19)
fix : bug 944 : multithreading with shared dictionary and large data, reported by gsliepen
cli : fix : content size written in header by default
cli : fix : improved LZ4 format support, by felixhandte
cli : new : hidden command `-S`, to benchmark multiple files while generating one result per file
api : fix : support large skippable frames, by terrelln
api : fix : streaming interface was adding a useless 3-bytes null block to small frames
api : change : when setting `pledgedSrcSize`, use `ZSTD_CONTENTSIZE_UNKNOWN` macro value to mean "unknown"
build: fix : compilation under rhel6 and centos6, reported by pixelb
build: added `check` target