Changes with nginx 1.17.9 03 Mar 2020
*) Change: now nginx does not allow several "Host" request header lines.
*) Bugfix: nginx ignored additional "Transfer-Encoding" request header lines.
*) Bugfix: socket leak when using HTTP/2.
*) Bugfix: a segmentation fault might occur in a worker process if OCSP stapling was used.
*) Bugfix: in the ngx_http_mp4_module.
*) Bugfix: nginx used status code 494 instead of 400 if errors with code 494 were redirected with the "error_page" directive.
*) Bugfix: socket leak when using subrequests in the njs module and the "aio" directive.