keyfile: relicense the code under LGPL-2.1+

Historically, keyfile read/write code was part of core, and thus
GPL-2.0+ licensed. Keyfile is the native file format for NetworkManager
connection profiles, and code to handle that should be part of libnm.
This would unlock many interesting features, like tools being able
to import/export connection profiles in the native file format.
However, libnm is LGPL-2.1+ licensed, so this is a problem.

The alternative would be to add a separate, GPL licensed library
(libnm-keyfile.so or libnm-gpl.so). That however also requires larger
rework, because the current keyfile implementation uses internal API
from libnm-core and it would need to use only public libnm API.

Relicense the code instead. According to research and "keyfile-history.sh"
script, the following individuals and companies may hold copyright
on the code:

  <bgalvani(at)redhat.com>
  <blueowl(at)centrum.cz>
  <daniel(at)gnoutcheff.name>
  <danw(at)redhat.com>
  <dcantrell(at)redhat.com>
  <dcbw(at)redhat.com>
  <evan(at)ebroder.net>
  <fgiudici(at)redhat.com>
  <floe(at)butterbrot.org>
  <j(at)bootlab.org>
  <kmaraas(at)gnome.org>
  <lkundrak(at)v3.sk>
  <luzpaz(at)users.noreply.github.com>
  <martinpitt(at)gnome.org>
  <michael.i.doherty(at)intel.com>
  <pavlix(at)pavlix.net>
  <pmarti(at)warp.es>
  <rafaelff(at)gnome.org>
  <rstrode(at)redhat.com>
  <tambet(at)gmail.com>
  <tgraf(at)redhat.com>
  <thaller(at)redhat.com>
  <walters(at)verbum.org>
  <yurchor(at)ukr.net>
  Red Hat, Inc.
  Novell, Inc.
  Intel Corporation
23 jobs for th/keyfile-relicense-as-lgpl in 46 minutes and 20 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
passed #5092804
checkpatch

00:02:03

manual #5092812
allowed to fail manual
t_centos:7.5.1804
manual #5092813
allowed to fail manual
t_centos:7.6.1810
manual #5092814
allowed to fail manual
t_centos:7.7.1908
manual #5092815
allowed to fail manual
t_centos:7.8.2003
manual #5092816
allowed to fail manual
t_centos:8.1.1911
manual #5092822
allowed to fail manual
t_debian:10
manual #5092821
allowed to fail manual
t_debian:9
manual #5092824
allowed to fail manual
t_debian:sid
manual #5092823
allowed to fail manual
t_debian:testing
manual #5092805
allowed to fail manual
t_fedora:28
manual #5092806
allowed to fail manual
t_fedora:29
manual #5092807
allowed to fail manual
t_fedora:30
manual #5092808
allowed to fail manual
t_fedora:31
passed #5092809
t_fedora:32

00:46:20

manual #5092810
allowed to fail manual
t_fedora:33
manual #5092811
allowed to fail manual
t_fedora:rawhide
manual #5092817
allowed to fail manual
t_ubuntu:16.04
manual #5092818
allowed to fail manual
t_ubuntu:18.04
manual #5092820
allowed to fail manual
t_ubuntu:devel
manual #5092819
allowed to fail manual
t_ubuntu:rolling
 
  External
failed https://desktopqe-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/beaker-NetworkManager-gitlab-trigger-code-upstream/1892/

failed https://desktopqe-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/beaker-NetworkManager-gitlab-trigger-code-upstream/1892/

07:17:20