Changes with nginx 1.7.12 07 Apr 2015
*) Feature: now the "tcp_nodelay" directive works with backend SSL connections.
*) Feature: now thread pools can be used to read cache file headers.
*) Bugfix: in the "proxy_request_buffering" directive.
*) Bugfix: a segmentation fault might occur in a worker process when using thread pools on Linux.
*) Bugfix: in error handling when using the "ssl_stapling" directive. Thanks to Filipe da Silva.
*) Bugfix: in the ngx_http_spdy_module.