zstd: Update to version 1.5.1

zstd: Update to version 1.5.1

- Update from 1.5.0 to 1.5.1
- Update of rootfile
- Changelog
   v1.5.1 (Dec, 2021)
     perf: rebalanced compression levels, to better match the intended speed/level curve,
           by @senhuang42
     perf: faster huffman decoder, using x64 assembly, by @terrelln
     perf: slightly faster high speed modes (strategies fast & dfast), by @felixhandte
     perf: improved binary size and faster compilation times, by @terrelln
     perf: new row64 mode, used notably in level 12, by @senhuang42
     perf: faster mid-level compression speed in presence of highly repetitive patterns,
           by @senhuang42
     perf: minor compression ratio improvements for small data at high levels, by @cyan4973
     perf: reduced stack usage (mostly useful for Linux Kernel), by @terrelln
     perf: faster compression speed on incompressible data, by @bindhvo
     perf: on-demand reduced ZSTD_DCtx state size, using build macro
           ZSTD_DECODER_INTERNAL_BUFFER, at a small cost of performance, by @bindhvo
     build: allows hiding static symbols in the dynamic library, using build macro,
            by @skitt
     build: support for m68k (Motorola 68000's), by @cyan4973
     build: improved AIX support, by @Helflym
     build: improved meson unofficial build, by @eli-schwartz
     cli : custom memory limit when training dictionary (#2925), by @embg
     cli : report advanced parameters information when compressing in very verbose mode
           (``-vv`), by @Svetlitski-FB

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>