Sun C complains about "statement not reached" if a "return" is followed
by additional statements.

Previously, the number of next_upstream tries included servers marked
as "down", resulting in "no live upstreams" with the code 502 instead
of the code derived from an attempt to connect to the last tried "up"
server (ticket #2096).

Similarly to ssl_conf_command, proxy_ssl_conf_command can be used to
set arbitrary OpenSSL configuration parameters as long as nginx is
compiled with OpenSSL 1.0.2 or later, when connecting to upstream
servers with SSL.  Full list of available configuration commands
can be found in the SSL_CONF_cmd manual page
(https://www.openssl.org/docs/man1.1.1/man3/SSL_CONF_cmd.html).

With the ssl_conf_command directive it is now possible to set
arbitrary OpenSSL configuration parameters as long as nginx is compiled
with OpenSSL 1.0.2 or later.  Full list of available configuration
commands can be found in the SSL_CONF_cmd manual page
(https://www.openssl.org/docs/man1.1.1/man3/SSL_CONF_cmd.html).

In particular, this allows configuring PrioritizeChaCha option
(ticket #1445):

    ssl_conf_command Options PrioritizeChaCha;

It can be also used to configure TLSv1.3 ciphers in OpenSSL,
which fails to configure them via the SSL_CTX_set_cipher_list()
interface (ticket #1529):

    ssl_conf_command Ciphersuites TLS_CHACHA20_POLY1305_SHA256;

Configuration commands are applied after nginx own configuration
for SSL, so they can be used to override anything set by nginx.
Note though that configuring OpenSSL directly with ssl_conf_command
might result in a behaviour nginx does not expect, and should be
done with care.

Adds 'set' directive to the stream server context.

Previously only an rbtree was associated with a limit_conn.  To make it
possible to associate more data with a limit_conn, shared context is introduced
similar to limit_req.  Also, shared pool pointer is kept in a way similar to
limit_req.

The variable takes one of the values: PASSED, REJECTED or REJECTED_DRY_RUN.

A new directive limit_conn_dry_run allows enabling the dry run mode.  In this
mode connections are not rejected, but reject status is logged as usual.

New variables $proxy_protocol_server_addr and $proxy_protocol_server_port are
added both to HTTP and Stream.