Blosc

In order to avoid problems with platforms with incomplete development
library codecs, the default is now to compile the internal codecs.
Users can still compile Blosc with external codecs by properly setting
cmake options like PREFER_EXTERNAL_SNAPPY, PREFER_EXTERNAL_ZLIB or
PREFER_EXTERNAL_ZSTD.

Also, the internal Zstd codec has been updated to 1.3.0.

For more info, please see the release notes in:

https://github.com/Blosc/c-blosc/blob/master/RELEASE_NOTES.rst

Enabled use as a CMake subproject, exporting shared & static library targets for super-projects to use. See PRs 178, 179 and 180. Thanks to Kevin Murray.

Also, internal codecs have been updated. LZ4 and LZ4HC codecs to 1.7.5 and Zstd to 1.1.2.

For more info, please see the release notes in:

https://github.com/Blosc/c-blosc/blob/master/RELEASE_NOTES.rst

=============================

* Internal C-Blosc sources updated to 1.21.2 (they are a git submodule now).

* Many small code improvements, improved consistency and typo fixes.
Thanks to Dimitri Papadopoulos Orfanos.

* Support for Python 3.11. Support for Python 3.7 has been dropped.
Thanks to Dimitri Papadopoulos Orfanos.

* Several other fixes, mainly related with the building process, which
should be more solid now in different situations.

=============================

* Add a missed cmake folder to distributed files. See 253.
Thanks to Ben Greiner.

=============================

- Reenable the possibility to use an already installed C-Blosc library.
See 244. Thanks to Ben Greiner.
- Add aarch64 wheels. See 250. Thanks to odidev.
- Deactivate SSE2 and AVX2 if a CPU has no flags. See 242.
Thanks to Graham Inggs.
- Wheels for Linux 32 bits are not distributed anymore.
- Updated vendored C-Blosc to 1.21.1.

=============================

* Update `blosc.nthreads` when `blosc.set_nthreads()` is called.
Fixes 246