file_utils.c: fix wrong licensing

liblxc has always been meant to be LGPLv2.1+ as reflected by the many
downstreams projects and bindings which are themselves under LGPLv2.1+ or other
licenses which would be incompatible with linking against a GPLv2+ library.

It's pretty normal for a library to be LGPL while binaries are GPL as a GPL
library would only ever be usable by other GPL-only projects, which isn't the
case for very many of the liblxc downstreams.

The issue here is really carelessness. None of those GPL headers were put there
intentionally, instead being wrongly copy/pasted from other parts of the
codebase which is indeed intended to be GPLv2+. This is also made clear in our
CONTRIBUTING file in this repository:

Licensing for new files:
------------------------

LXC is made of files shipped under a few different licenses.

Anything that ends up being part of the LXC library needs to be released
under LGPLv2.1+ or a license compatible with it (though the latter will
only be accepted for cases where the code originated elsewhere and was
imported into LXC).

Language bindings for the libraries need to be released under LGPLv2.1+.

Anything else (non-libraries) needs to be Free Software and needs to be
allowed to link with LGPLv2.1+ code (if needed). LXC upstream prefers
LGPLv2.1+ or GPLv2 for those.

When introducing a new file into the project, please make sure it has a
copyright header making clear under which license it's being released
and if it doesn't match the criteria described above, please explain
your decision on the lxc-devel mailing-list when submitting your patch.

This is intended to switch over files to LGPLv2.1+ to which end we have
collected ACKs from relevant people.
/* Affected People */
Christian Brauner <christian.brauner@ubuntu.com>
Donghwa Jeong <dh48.jeong@samsung.com>

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Donghwa Jeong <dh48.jeong@samsung.com>

src/lxc/file_utils.c

@@ -1,20 +1,21 @@
 /* liblxcapi
  *
- * Copyright © 2018 Christian Brauner <christian.brauner@ubuntu.com>.
- * Copyright © 2018 Canonical Ltd.
+ * Copyright © 2019 Christian Brauner <christian.brauner@ubuntu.com>.
+ * Copyright © 2019 Canonical Ltd.
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2, as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+
+ * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 #ifndef _GNU_SOURCE