- 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
Adds 'code' to the list of suffixes that are excluded from version
parsing of URLs, such that if a URL contains the string
'cistem-1.0.0-beta-source-code', a version X will substitute in to
produce a URL with cistem-X-source-code ('source' was already excluded).
The 'cistem' package version is updated to make use of this (and fix
a fetching bug with the cistem package). A unit test is added to check
this parsing case.
