parse-datetime: use the module from gnulib

Use the parse-datetime module from gnulib, and adapt it to not require
other modules as portability is not really an issue for us.

DATE can be specified in different formats, such as: "-1 week", "last
monday", "1 week ago".

Include the generated .c file in the repository so to not add another
dependency to Bison.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

src/ostree/parse-datetime.h

@@ -1,31 +1,22 @@
-/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
- *
- * Copyright (C) 2015 Red Hat, Inc.
- *
- * 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 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
- * 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., 59 Temple Place - Suite 330,
- * Boston, MA 02111-1307, USA.
- */
+/* Parse a string into an internal time stamp.
 
-#pragma once
+   Copyright (C) 1995, 1997-1998, 2003-2004, 2007, 2009-2015 Free Software
+   Foundation, Inc.
+
+   This program 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 of the License, or
+   (at your option) any later version.
+
+   This program 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, see <http://www.gnu.org/licenses/>.  */
 
-#include "config.h"
-#include <gio/gio.h>
 #include <stdbool.h>
 #include <time.h>
-#include <stdbool.h>
 
-G_BEGIN_DECLS
 bool parse_datetime (struct timespec *, char const *, struct timespec const *);
-G_END_DECLS