* express: new version, use tags and fix gcc@6.0.0:
Express fails to build with gcc@6.0.0:.
The debian project [has a
fix](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=811859) but
they don't seem to have pushed it upstream.
I've opened an issue and a PR in eXpress repo, but eXpress isn't
actively developed, so I'm fixing it here too.
Since the Spack package was created, the eXpress team tagged their
releases. I've updated the package to use the tags.
Version 1.5.1 used to be known as 2015-11-29 (same commit). 1.5.2 is
new(er).
* Make flake8 happ{y,ier}
- 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
