*: change C-style prototypes, drop "(void)"

src/playlist/PlaylistPlugin.hxx

@@ -44,7 +44,7 @@ struct playlist_plugin {
 	 * Deinitialize a plugin which was initialized successfully.
 	 * Optional method.
 	 */
-	void (*finish)(void);
+	void (*finish)();
 
 	/**
 	 * Opens the playlist on the specified URI.  This URI has

src/playlist/PlaylistRegistry.hxx

@@ -37,13 +37,13 @@ extern const struct playlist_plugin *const playlist_plugins[];
  * Initializes all playlist plugins.
  */
 void
-playlist_list_global_init(void);
+playlist_list_global_init();
 
 /**
  * Deinitializes all playlist plugins.
  */
 void
-playlist_list_global_finish(void);
+playlist_list_global_finish();
 
 /**
  * Opens a playlist by its URI.