https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/784

"libnm-platform" has no dependency on libnm-core. To have the symbols
accessible, move them to libnm-base.

Like with "libnm-core/", split "libnm/" into different directories for
the public headers, for the implementation and for the helper "aux"
library.

"libnm-core/" is rather complicated. It provides a static library that
is linked into libnm.so and NetworkManager. It also contains public
headers (like "nm-setting.h") which are part of public libnm API.

Then we have helper libraries ("libnm-core/nm-libnm-core-*/") which
only rely on public API of libnm-core, but are themself static
libraries that can be used by anybody who uses libnm-core. And
"libnm-core/nm-libnm-core-intern" is used by libnm-core itself.

Move "libnm-core/" to "src/". But also split it in different
directories so that they have a clearer purpose.

The goal is to have a flat directory hierarchy. The "src/libnm-core*/"
directories correspond to the different modules (static libraries and set
of headers that we have). We have different kinds of such modules because
of how we combine various code together. The directory layout now reflects
this.

We want to use these defines for option names also in "shared/nm-base"
(and in turn in "shared/nm-platform), which cannot include "libnm-core".

However, they are also public API of libnm.

To get this done, in a first step, move these defines to a new header
"libnm-core/nm-ethtool-utils.h".

Since now the name "nm-ethtool-utils.h" is taken, also rename
nm-libnm-core-intern files.

These SPDX license identifiers are deprecated ([1]). Update them.

[1] https://spdx.org/licenses/

  sed \
     -e '1 s%^/\* SPDX-License-Identifier: \(GPL-2.0\|LGPL-2.1\)+ \*/$%/* SPDX-License-Identifier: \1-or-later */%' \
     -e '1,2 s%^\(--\|#\|//\) SPDX-License-Identifier: \(GPL-2.0\|LGPL-2.1\)+$%\1 SPDX-License-Identifier: \2-or-later%' \
     -i \
     $(git grep -l SPDX-License-Identifier -- \
         ':(exclude)shared/c-*/' \
         ':(exclude)shared/n-*/' \
         ':(exclude)shared/systemd/src' \
         ':(exclude)src/systemd/src')

https://bugzilla.redhat.com/show_bug.cgi?id=1867997
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/ ## 600