* Add stat version 4.0.1
* stat 4.0.1: requires py-xdot
* stat versions at or above 4.0.0 dont require python 2 (it still
requires python but can build with 2 or 3)
* stat versions at or above 4.0.0 dont require py-pygtk and py-enum34
* Replace py-xdot version 0.9.1 with 1.0
* py-xdot: use lib directory vs. lib64 for atk dependency
- 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
