Cache: support for stale-while-revalidate and stale-if-error. Previously, there was no way to enable the proxy_cache_use_stale behavior by reading the backend response. Now, stale-while-revalidate and stale-if-error Cache-Control extensions (RFC 5861) are supported. They specify, how long a stale response can be used when a cache entry is being updated, or in case of an error.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


cat << END >> $NGX_AUTO_CONFIG_H

#ifndef $have
#define $have  1
#endif

END