Implement notification_create function

notification_create currently simply allocates memory and zeroes it to
properly initialise a notification. Since we currently have at least 2
places in the code that create notifications(startup notification in
dunst.c and notifications from dbus in dbus.c) the creation should be
handled from a central location in case we ever need to change the
creation procedure later on.

src/dbus.c

@@ -295,7 +295,7 @@ static void onNotify(GDBusConnection * connection,
                 }
         }
 
-        notification *n = malloc(sizeof(notification));
+        notification *n = notification_create();
         if(n == NULL) {
                 die("Unable to allocate memory", EXIT_FAILURE);
         }

src/dunst.c

@@ -343,7 +343,7 @@ int dunst_main(int argc, char *argv[])
         x_setup();
 
         if (settings.startup_notification) {
-                notification *n = malloc(sizeof(notification));
+                notification *n = notification_create();
                 if(n == NULL) {
                         die("Unable to allocate memory", EXIT_FAILURE);
                 }

src/notification.c

@@ -311,6 +311,20 @@ char *notification_extract_markup_urls(char **str_ptr) {
     return urls;
 }
 
+/*
+ * This is a helper function that allocates, initialises a notification and
+ * returns a pointer to it. All notifications should be created using this
+ * function. After setting all the necessary fields(i.e. appname, summary,
+ * body, icon etc) notification_init should be called to do the actual
+ * initialisation.
+ */
+notification *notification_create(void)
+{
+        notification *n = malloc(sizeof(notification));
+        memset(n, 0, sizeof(notification));
+        return n;
+}
+
 /*
  * Initialize the given notification and add it to
  * the queue. Replace notification with id if id > 0.

src/notification.h

@@ -54,6 +54,7 @@ typedef struct _notification {
         Actions *actions;
 } notification;
 
+notification *notification_create(void);
 int notification_init(notification * n, int id);
 void notification_free(notification * n);
 int notification_close_by_id(int id, int reason);