Threads: offloading of temp files writing to thread pools. The ngx_thread_write_chain_to_file() function introduced, which uses ngx_file_t thread_handler, thread_ctx and thread_task fields. The task context structure (ngx_thread_file_ctx_t) is the same for both reading and writing, and can be safely shared as long as operations are serialized. The task->handler field is now always set (and not only when task is allocated), as the same task can be used with different handlers. The thread_write flag is introduced in the ngx_temp_file_t structure to explicitly enable use of ngx_thread_write_chain_to_file() in ngx_write_chain_to_temp_file() when supported by caller. In collaboration with Valentin Bartenev.

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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;