Queue: ModifyAtOrder() does not increment version

Leave that to the caller, allowing it to modify multiple items at a
time.

src/Playlist.cxx

@@ -48,6 +48,7 @@ playlist::TagModified(Song &&song)
 		current_song.ReplaceTag(std::move(*song.tag));
 
 	queue.ModifyAtOrder(current);
+	queue.IncrementVersion();
 	idle_add(IDLE_PLAYLIST);
 }
 

src/Queue.cxx

@@ -83,8 +83,6 @@ queue::ModifyAtOrder(unsigned _order)
 
 	unsigned position = order[_order];
 	items[position].version = version;
-
-	IncrementVersion();
 }
 
 void

src/Queue.hxx

@@ -241,7 +241,8 @@ struct queue {
 	void IncrementVersion();
 
 	/**
-	 * Marks the specified song as "modified" and increments the version
+	 * Marks the specified song as "modified".  Call
+	 * IncrementVersion() after all modifications have been made.
 	 * number.
 	 */
 	void ModifyAtOrder(unsigned order);