Changes with nginx 1.7.8 02 Dec 2014

    *) Change: now the "If-Modified-Since", "If-Range", etc. client request
       header lines are passed to a backend while caching if nginx knows in
       advance that the response will not be cached (e.g., when using
       proxy_cache_min_uses).

    *) Change: now after proxy_cache_lock_timeout nginx sends a request to a
       backend with caching disabled; the new directives
       "proxy_cache_lock_age", "fastcgi_cache_lock_age",
       "scgi_cache_lock_age", and "uwsgi_cache_lock_age" specify a time
       after which the lock will be released and another attempt to cache a
       response will be made.

    *) Change: the "log_format" directive can now be used only at http
       level.

    *) Feature: the "proxy_ssl_certificate", "proxy_ssl_certificate_key",
       "proxy_ssl_password_file", "uwsgi_ssl_certificate",
       "uwsgi_ssl_certificate_key", and "uwsgi_ssl_password_file"
       directives.
       Thanks to Piotr Sikora.

    *) Feature: it is now possible to switch to a named location using
       "X-Accel-Redirect".
       Thanks to Toshikuni Fukaya.

    *) Feature: now the "tcp_nodelay" directive works with SPDY connections.

    *) Feature: new directives in vim syntax highliting scripts.
       Thanks to Peter Wu.

    *) Bugfix: nginx ignored the "s-maxage" value in the "Cache-Control"
       backend response header line.
       Thanks to Piotr Sikora.

    *) Bugfix: in the ngx_http_spdy_module.
       Thanks to Piotr Sikora.

    *) Bugfix: in the "ssl_password_file" directive when using OpenSSL
       0.9.8zc, 1.0.0o, 1.0.1j.

    *) Bugfix: alerts "header already sent" appeared in logs if the
       "post_action" directive was used; the bug had appeared in 1.5.4.

    *) Bugfix: alerts "the http output chain is empty" might appear in logs
       if the "postpone_output 0" directive was used with SSI includes.

    *) Bugfix: in the "proxy_cache_lock" directive with SSI subrequests.
       Thanks to Yichun Zhang.