Features
   * Add getter (mbedtls_ssl_cache_get_timeout()) to access
     `mbedtls_ssl_cache_context.timeout`.
   * Add getter (mbedtls_ssl_get_hostname()) to access
     `mbedtls_ssl_context.hostname`.
   * Add getter (mbedtls_ssl_conf_get_endpoint()) to access
     `mbedtls_ssl_config.endpoint`.