Log Message:
zstd: updated to 1.3.8

Zstandard v1.3.8
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
api : support decompression of empty frames into NULL (used to be an error)
build: new set of build macros to generate a minimal size decoder
build: fix compilation on MIPS32
build: fix compilation with multiple -arch flags
build: highly upgraded meson build
build: improved buck support
build: fix cmake script : can create debug build
build: Makefile : grep works on both colored consoles and systems without color \ 
support
build: fixed zstd-pgo target
cli : support ZSTD_CLEVEL environment variable
cli : --no-progress flag, preserving final summary
cli : ensure destination file is not source file
cli : clearer error messages, notably when input file not present
doc : clarified zstd_compression_format.md
misc: fixed zstdgrep, returns 1 on failure
misc: NEWS renamed as CHANGELOG, in accordance with fb.oss policy