Add support for snoozing alarms

Also modified time_manager to pass time by value to time callbacks as
it's a fairly small struct and it will probably be more robust.

components/time/time_manager.c

@@ -38,7 +38,7 @@ static void run_callbacks(void *arg)
 {
 	const Time time = get_time();
 	for (unsigned i = 0; i < callback_count; ++i)
-		callbacks[i](&time);
+		callbacks[i](time);
 }
 
 static int time_command_func(int argc, char **argv)

components/time/time_manager.h

@@ -28,7 +28,7 @@ typedef enum {
 	WEEK_DAY_SUNDAY,
 } WeekDay;
 
-typedef void (*TimeCallback)(const Time *time);
+typedef void (*TimeCallback)(Time now);
 
 /**
  * Initialize the time module.