license: merge branch 'th/fix-gpl-license'

Change the license for a few files from GPL-2.0-only to
LGPL-2.1-only.

All relevant contributions seems to have been made by Thomas Graf. I
presume, this was just a mistake in the license header, as the project
as a whole is LGPL licensed. Thomas as working for Red Hat at the time,
maybe the copyright for the code is with Red Hat.

In any case, the wrong licensing needs to be fixed. If there are any
objections to this, the offending code needs to be removed. Please reach
out in that case.

#357

src/nl-addr-add.c

@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
+/* SPDX-License-Identifier: LGPL-2.1-only */
 /*
  * Copyright (c) 2003-2009 Thomas Graf <tgraf@suug.ch>
  */

src/nl-addr-delete.c

@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
+/* SPDX-License-Identifier: LGPL-2.1-only */
 /*
  * Copyright (c) 2003-2009 Thomas Graf <tgraf@suug.ch>
  */

src/nl-addr-list.c

@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
+/* SPDX-License-Identifier: LGPL-2.1-only */
 /*
  * Copyright (c) 2003-2009 Thomas Graf <tgraf@suug.ch>
  */

src/nl-cls-add.c

@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
+/* SPDX-License-Identifier: LGPL-2.1-only */
 /*
  * Copyright (c) 2003-2011 Thomas Graf <tgraf@suug.ch>
  */