- remove the old LGPL license headers from all files in Spack
- add SPDX headers to all files
- core and most packages are (Apache-2.0 OR MIT)
- a very small number of remaining packages are LGPL-2.1-only
* A new package: perl-compress-raw-zlib.
* A new package: perl-compress-raw-bzip2.
* A new perl package: perl-io-compress.
* flake8.
* Add zlib and bzip2 dependency.