Updated: zstd-1.5.6-1 and development headers / libraries

[ASSI]

This release updates Zstandard to the latest upstream version, which is
a maintenance release with bugfixes and minor performance improvements.


Zstandard, or zstd as short version, is a fast lossless compression
algorithm, targeting real-time compression scenarios at zlib-level and
better compression ratios.

http://www.zstd.net/


Besides a standalone compression tool, development headers and a library
with comprehensive API are available both for Cygwin native applications
and cross-compilation toolchains in the following sub-packages:

libzstd-devel-1.5.6-1
libzstd1-1.5.6-1
mingw64-i686-zstd-1.5.6-1
mingw64-x86_64-zstd-1.5.6-1

Notes
-----

This version is compiled with support for GZip, LZ4 and Xz compression
and all libraries are built with MT capability.  Support for legacy
formats from ZStandard versions before 1.0 has been removed.

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