Log Message:
zstd: update to 1.4.0.

v1.4.0
perf: Improve level 1 compression speed in most scenarios by 6% by @gbtucker and \ 
@terrelln
api: Move the advanced API, including all functions in the staging section, to \ 
the stable section
api: Make ZSTD_e_flush and ZSTD_e_end block for maximum forward progress
api: Rename ZSTD_CCtxParam_getParameter to ZSTD_CCtxParams_getParameter
api: Rename ZSTD_CCtxParam_setParameter to ZSTD_CCtxParams_setParameter
api: Don't export ZSTDMT functions from the shared library by default
api: Require ZSTD_MULTITHREAD to be defined to use ZSTDMT
api: Add ZSTD_decompressBound() to provide an upper bound on decompressed size \ 
by @shakeelrao
api: Fix ZSTD_decompressDCtx() corner cases with a dictionary
api: Move ZSTD_getDictID_*() functions to the stable section
api: Add ZSTD_c_literalCompressionMode flag to enable or disable literal \ 
compression by @terrelln
api: Allow compression parameters to be set when a dictionary is used
api: Allow setting parameters before or after ZSTD_CCtx_loadDictionary() is called
api: Fix ZSTD_estimateCStreamSize_usingCCtxParams()
api: Setting ZSTD_d_maxWindowLog to 0 means use the default
cli: Ensure that a dictionary is not used to compress itself by @shakeelrao
cli: Add --[no-]compress-literals flag to enable or disable literal compression
doc: Update the examples to use the advanced API
doc: Explain how to transition from old streaming functions to the advanced API \ 
in the header
build: Improve the Windows release packages
build: Improve CMake build by @hjmjohnson
build: Build fixes for FreeBSD by @lwhsu
build: Remove redundant warnings by @thatsafunnyname
build: Fix tests on OpenBSD by @bket
build: Extend fuzzer build system to work with the new clang engine
build: CMake now creates the libzstd.so.1 symlink
build: Improve Menson build by @lzutao
misc: Fix symbolic link detection on FreeBSD
misc: Use physical core count for -T0 on FreeBSD by @cemeyer
misc: Fix zstd --list on truncated files by @kostmo
misc: Improve logging in debug mode by @felixhandte
misc: Add CirrusCI tests by @lwhsu
misc: Optimize dictionary memory usage in corner cases
misc: Improve the dictionary builder on small or homogeneous data
misc: Fix spelling across the repo by @jsoref