clock: introduce GcalClock

GcalClock is an internal clock for GNOME Calendar that
sends a few utility signals, such as :day-changed and
:minute-changed.

It also watches for suspend/resume events to properly
send the signal right after the resume.

src/gcal-clock.h

@@ -0,0 +1,35 @@
+/* gcal-clock.h
+ *
+ * Copyright (C) 2017 Georges Basile Stavracas Neto <georges.stavracas@gmail.com>
+ *
+ * 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 3 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/>.
+ */
+
+#ifndef GCAL_CLOCK_H
+#define GCAL_CLOCK_H
+
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define GCAL_TYPE_CLOCK (gcal_clock_get_type())
+
+G_DECLARE_FINAL_TYPE (GcalClock, gcal_clock, GCAL, CLOCK, GObject)
+
+GcalClock*           gcal_clock_new                              (void);
+
+G_END_DECLS
+
+#endif /* GCAL_CLOCK_H */
+