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')

Part of !537.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/537

```bash

readarray -d '' FILES < <(
  git ls-files -z \
    ':(exclude)po' \
    ':(exclude)shared/c-rbtree' \
    ':(exclude)shared/c-list' \
    ':(exclude)shared/c-siphash' \
    ':(exclude)shared/c-stdaux' \
    ':(exclude)shared/n-acd' \
    ':(exclude)shared/n-dhcp4' \
    ':(exclude)src/systemd/src' \
    ':(exclude)shared/systemd/src' \
    ':(exclude)m4' \
    ':(exclude)COPYING*'
  )

sed \
  -e 's/^\(--\|#\| \*\) *\(([cC]) *\)\?Copyright \+\(\(([cC])\) \+\)\?\(\(20\|19\)[0-9][0-9]\) *[-–] *\(\(20\|19\)[0-9][0-9]\) \+\([^ ].*\)$/\1 C1pyright#\5 - \7#\9/' \
  -e 's/^\(--\|#\| \*\) *\(([cC]) *\)\?Copyright \+\(\(([cC])\) \+\)\?\(\(20\|19\)[0-9][0-9]\) *[,] *\(\(20\|19\)[0-9][0-9]\) \+\([^ ].*\)$/\1 C2pyright#\5, \7#\9/' \
  -e 's/^\(--\|#\| \*\) *\(([cC]) *\)\?Copyright \+\(\(([cC])\) \+\)\?\(\(20\|19\)[0-9][0-9]\) \+\([^ ].*\)$/\1 C3pyright#\5#\7/' \
  -e 's/^Copyright \(\(20\|19\)[0-9][0-9]\) \+\([^ ].*\)$/C4pyright#\1#\3/' \
  -i \
  "${FILES[@]}"

echo ">>> untouched Copyright lines"
git grep Copyright "${FILES[@]}"

echo ">>> Copyright lines with unusual extra"
git grep '\<C[0-9]pyright#' "${FILES[@]}" | grep -i reserved

sed \
  -e 's/\<C[0-9]pyright#\([^#]*\)#\(.*\)$/Copyright (C) \1 \2/' \
  -i \
  "${FILES[@]}"

```

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/merge_requests/298

  $ find * -type f |xargs perl contrib/scripts/spdx.pl
  $ git rm contrib/scripts/spdx.pl

  sed '1,3 { /^\(#\|--\) *vim:/d }; 1 { /^\/\* *vim:.*\*\/$/ d}' -i $(git grep -l 'vim:')

We no longer add these. If you use Emacs, configure it yourself.

Also, due to our "smart-tab" usage the editor anyway does a subpar
job handling our tabs. However, on the upside every user can choose
whatever tab-width he/she prefers. If "smart-tabs" are used properly
(like we do), every tab-width will work.

No manual changes, just ran commands:

    F=($(git grep -l -e '-\*-'))
    sed '1 { /\/\* *-\*-  *[mM]ode.*\*\/$/d }'     -i "${F[@]}"
    sed '1,4 { /^\(#\|--\|dnl\) *-\*- [mM]ode/d }' -i "${F[@]}"

Check remaining lines with:

    git grep -e '-\*-'

The ultimate purpose of this is to cleanup our files and eventually use
SPDX license identifiers. For that, first get rid of the boilerplate lines.

https://bugzilla.gnome.org/show_bug.cgi?id=791121

gi now emits a warning when not loading a specific library
version [1]:

  ./generate-setting-docs.py:21: PyGIWarning: NM was imported without specifying a version first. Use gi.require_version(NM, 1.0) before import to ensure that the right version gets loaded.
    from gi.repository import NM, GObject

Seems require_version() is reasonably old to just always use it without
breaking on older versions [2].

[1] Related: https://bugzilla.gnome.org/show_bug.cgi?id=727379
[2] https://git.gnome.org/browse/pygobject/commit/?id=76758efb6579752237a0dc4d56cf9518de6c6e55