Queue: move HASH_MULT and Item into the Queue class

src/Queue.hxx

@@ -28,19 +28,28 @@
 #include <assert.h>
 #include <stdint.h>
 
-enum {
+/**
+ * A queue of songs.  This is the backend of the playlist: it contains
+ * an ordered list of songs.
+ *
+ * Songs can be addressed in three possible ways:
+ *
+ * - the position in the queue
+ * - the unique id (which stays the same, regardless of moves)
+ * - the order number (which only differs from "position" in random mode)
+ */
+struct queue {
 	/**
 	 * reserve max_length * QUEUE_HASH_MULT elements in the id
 	 * number space
 	 */
-	QUEUE_HASH_MULT = 4,
+	static constexpr unsigned QUEUE_HASH_MULT = 4;
-};
 
-/**
+	/**
 	 * One element of the queue: basically a song plus some queue specific
 	 * information attached.
 	 */
-struct queue_item {
+	struct queue_item {
 		struct song *song;
 
 		/** the unique id of this item in the queue */
@@ -55,19 +64,8 @@ struct queue_item {
 		 * "random" mode.
 		 */
 		uint8_t priority;
-};
+	};
 
-/**
- * A queue of songs.  This is the backend of the playlist: it contains
- * an ordered list of songs.
- *
- * Songs can be addressed in three possible ways:
- *
- * - the position in the queue
- * - the unique id (which stays the same, regardless of moves)
- * - the order number (which only differs from "position" in random mode)
- */
-struct queue {
 	/** configured maximum length of the queue */
 	unsigned max_length;