sasl_client_add_plugin
LIBSASL_API int sasl_client_add_plugin(const char *plugname,
{ "sasl_client_plug_init", (add_plugin_t *)sasl_client_add_plugin },
sasl_client_add_plugin("EXTERNAL", &external_client_plug_init);
add_plugin = (add_plugin_t *)sasl_client_add_plugin;