stream {
    limit_conn_zone $binary_remote_addr zone=perip:1m;
    limit_conn_log_level error;

    server {
        ...
        limit_conn perip 1;
    }
}

It's now initialized in auto/options like the rest of variables
for system paths.

As a side effect, the currently unused macro NGX_SBIN_PATH now
gets the correct value.

stream {
    server {
        ...
        allow 127.0.0.1;
        deny all;
    }
}

Removed the deprecated --without-http_limit_zone_module option.
Deprecated the --with-imap and --with-imap_ssl_module options.

Upstreams with the "zone" directive are kept in shared memory,
with a consistent view of all worker processes.