Log Message:
nginx-devel: updated to 1.21.4

Changes with nginx 1.21.4

*) Change: support for NPN instead of ALPN to establish HTTP/2
   connections has been removed.

*) Change: now nginx rejects SSL connections if ALPN is used by the
   client, but no supported protocols can be negotiated.

*) Change: the default value of the "sendfile_max_chunk" directive was
   changed to 2 megabytes.

*) Feature: the "proxy_half_close" directive in the stream module.

*) Feature: the "ssl_alpn" directive in the stream module.

*) Feature: the $ssl_alpn_protocol variable.

*) Feature: support for SSL_sendfile() when using OpenSSL 3.0.

*) Feature: the "mp4_start_key_frame" directive in the
   ngx_http_mp4_module.
   Thanks to Tracey Jaquith.

*) Bugfix: in the $content_length variable when using chunked transfer
   encoding.

*) Bugfix: after receiving a response with incorrect length from a
   proxied backend nginx might nevertheless cache the connection.
   Thanks to Awdhesh Mathpal.

*) Bugfix: invalid headers from backends were logged at the "info" level
   instead of "error"; the bug had appeared in 1.21.1.

*) Bugfix: requests might hang when using HTTP/2 and the "aio_write"
   directive.