C-Blosc 1.21.1 released

Changes from 1.21.0 to 1.21.1

• Fix pthread flag when linking on ppc64le. See #318. Thanks to Axel Huebl.

• Updates in codecs (some bring important performance improvements):

  • BloscLZ updated to 2.5.1
  • Zlib updated to 1.2.11
  • Zstd updated to 1.5.0