+/**
+* @brief Load plugins according to an index file.
+*
+* @details Builds an ArrayList of plugin servers only if there is no
+* mismatch for file layout version, index identifier, or timestamp of
+* the built-in plugins. If OK, add the plugin servers to the global list.
+*
+* @note If an error is returned the index file needs to be rebuilt, and
+* then this function must be called again.
+* There are two types of index files, with the same layout internally.
+* One called "Cinelerra_plugins" for built-ins, ffmpeg and lv2 .
+* The other type "ladspa_plugins.index_id" where index_id is either the
+* path or the $CIN_BUILD identifier if the path is from the running
+* AppImage itself. If there are multiple ladspa directories in the
+* path, there will be multiple index files.
+*
+* @return -1 if file no open, 0 if OK, 1 if error.
+*/
+int MWindow::load_plugin_index(MWindow *mwindow, FILE *fp, const char *plugin_dir, const char *index_id)