Changes with nginx 1.13.7 21 Nov 2017
*) Bugfix: in the $upstream_status variable.
*) Bugfix: a segmentation fault might occur in a worker process if a backend returned a "101 Switching Protocols" response to a subrequest.
*) Bugfix: a segmentation fault occurred in a master process if a shared memory zone size was changed during a reconfiguration and the reconfiguration failed.
*) Bugfix: in the ngx_http_fastcgi_module.
*) Bugfix: nginx returned the 500 error if parameters without variables were specified in the "xslt_stylesheet" directive.
*) Workaround: "gzip filter failed to use preallocated memory" alerts appeared in logs when using a zlib library variant from Intel.
*) Bugfix: the "worker_shutdown_timeout" directive did not work when using mail proxy and when proxying WebSocket connections.