Mainly focus on files that use BSD 2-Clause license, however the tool I
was using mis-identified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
Even though these header files make little sense to me, they are part of
the standard. By including these header files, you can simply use
`alignas', `alignof' and `noreturn' instead of the underscore-prefixed
versions.