1.20.0 (beast) release

Changes from 1.19.1 to 1.20.0

• More saftey checks have been implemented so that potential flaws
  discovered by new fuzzers in OSS-Fuzzer are fixed now. Thanks to
  Nathan Moinvaziri (@nmoinvaz).

• BloscLZ updated to 2.3.0. Expect better compression ratios for faster
  codecs. For details, see our new blog post:
  https://blosc.org/posts/beast-release/

• Fixed the _xgetbv() collision. Thanks to Michał Górny (@mgorny).

• The chunk format has been fully described so that 3rd party software
  may come with a different implementation, but still compatible with
  C-Blosc chunks.