wayland: Add common object for device classes

Add a new object class, MetaWaylandInputDevice, and make all device
classes (pointer, keyboard, touch) inherit it. In the future common
functionality may be placed there.

https://bugzilla.gnome.org/show_bug.cgi?id=771305

src/wayland/meta-wayland-input-device.c

@@ -0,0 +1,41 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/*
+ * Copyright (C) 2016 Red Hat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ * Written by:
+ *     Jonas Ådahl <jadahl@gmail.com>
+ */
+
+#include "config.h"
+
+#include "wayland/meta-wayland-input-device.h"
+
+G_DEFINE_TYPE (MetaWaylandInputDevice,
+               meta_wayland_input_device,
+               G_TYPE_OBJECT)
+
+static void
+meta_wayland_input_device_init (MetaWaylandInputDevice *input_device)
+{
+}
+
+static void
+meta_wayland_input_device_class_init (MetaWaylandInputDeviceClass *klass)
+{
+}