Gzip: fixed "zero size buf" alerts after ac5a741d39cf. After ac5a741d39cf it is now possible that after zstream.avail_out reaches 0 and we allocate additional buffer, there will be no more data to put into this buffer, triggering "zero size buf" alert. Fix is to reset b->temporary flag in this case. Additionally, an optimization added to avoid allocating additional buffer in this case, by checking if last deflate() call returned Z_STREAM_END. Note that checking for Z_STREAM_END by itself is not enough to fix alerts, as deflate() can return Z_STREAM_END without producing any output if the buffer is smaller than gzip trailer. Reported by Witold Filipczyk, http://mailman.nginx.org/pipermail/nginx-devel/2019-July/012469.html.

uwsgi_param  QUERY_STRING       $query_string;
uwsgi_param  REQUEST_METHOD     $request_method;
uwsgi_param  CONTENT_TYPE       $content_type;
uwsgi_param  CONTENT_LENGTH     $content_length;

uwsgi_param  REQUEST_URI        $request_uri;
uwsgi_param  PATH_INFO          $document_uri;
uwsgi_param  DOCUMENT_ROOT      $document_root;
uwsgi_param  SERVER_PROTOCOL    $server_protocol;
uwsgi_param  REQUEST_SCHEME     $scheme;
uwsgi_param  HTTPS              $https if_not_empty;

uwsgi_param  REMOTE_ADDR        $remote_addr;
uwsgi_param  REMOTE_PORT        $remote_port;
uwsgi_param  SERVER_PORT        $server_port;
uwsgi_param  SERVER_NAME        $server_name;