- 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
somatic-sniper installs its own copy of samtools, which needs curses.
I'm not sure why I didn't stumble on this in my dev environment, but I
just stumbled over it in a standalone build.
