+/** @brief Add a track to the queue
+ * @param track Track to add
+ * @param submitter Who added it, or NULL
+ * @param where Where to add it
+ * @param target ID to add after for @ref WHERE_AFTER
+ * @param origin Track origin
+ * @return New queue entry or NULL
+ *
+ * The queue is NOT saved to disk.
+ *
+ * NULL can only be returned if @ref WHERE_AFTER is used with an invalid
+ * queue ID.
+ */