- 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
* Add a new package for Open Babel
* Add post-installation tests, stolen from the fine folks at Homebrew
* Add patch to fix Python 3.6 support
* Add a more complete patch to get Python 3.6 support working
* Add patch to convert tabs to spaces in test script
testpdbformat.py contains mixed tabs and spaces
causing the unit tests to fail. With this patch,
all tests pass with flying colors.
