message: use buffer_stack
diff: @@ -1881,13 +1881,14 @@ static void http_build_header(http_context *ctx, zval *object, swString *respons
  swServer *serv = SwooleG.serv;
  char *buf = SwooleTG.buffer_stack->str;
  + size_t l_buf = SwooleTG.buffer_stack->size;
  int n;
  char *date_str;
  /**
  * http status line
  */
  - n = snprintf(buf, sizeof(buf), "HTTP/1.1 %s\r\n", http_status_message(ctx->response.status));
  + n = snprintf(buf, l_buf, "HTTP/1.1 %s\r\n", http_status_message(ctx->response.status));
  swString_append_ptr(response, buf, n);
  /**
  @@ -1925,7 +1926,7 @@ static void http_build_header(http_context *ctx, zval *object, swString *respons
  {
  flag |= HTTP_RESPONSE_CONTENT_TYPE;
  }
  - n = snprintf(buf, sizeof(buf), "%*s: %*s\r\n", keylen - 1, key, (int)Z_STRLEN_P(value), Z_STRVAL_P(value));
  + n = snprintf(buf, l_buf, "%*s: %*s\r\n", keylen - 1, key, (int)Z_STRLEN_P(value), Z_STRVAL_P(value));
  swString_append_ptr(response, buf, n);
  }
  SW_HASHTABLE_FOREACH_END();
  @@ -1960,7 +1961,7 @@ static void http_build_header(http_context *ctx, zval *object, swString *respons
  if (!(flag & HTTP_RESPONSE_DATE))
  {
  date_str = sw_php_format_date(ZEND_STRL(SW_HTTP_DATE_FORMAT), serv->gs->now, 0 TSRMLS_CC);
  - n = snprintf(buf, sizeof(buf), "Date: %s\r\n", date_str);
  + n = snprintf(buf, l_buf, "Date: %s\r\n", date_str);
  swString_append_ptr(response, buf, n);
  efree(date_str);
  }
  @@ -1979,7 +1980,7 @@ static void http_build_header(http_context *ctx, zval *object, swString *respons
  }
  //Date
  date_str = sw_php_format_date(ZEND_STRL(SW_HTTP_DATE_FORMAT), serv->gs->now, 0 TSRMLS_CC);
  - n = snprintf(buf, sizeof(buf), "Date: %s\r\n", date_str);
  + n = snprintf(buf, l_buf, "Date: %s\r\n", date_str);
  efree(date_str);
  swString_append_ptr(response, buf, n);
  }
  @@ -2001,7 +2002,7 @@ static void http_build_header(http_context *ctx, zval *object, swString *respons
  body_length = swoole_zlib_buffer->length;
  }
  #endif
  - n = snprintf(buf, sizeof(buf), "Content-Length: %d\r\n", body_length);
  + n = snprintf(buf, l_buf, "Content-Length: %d\r\n", body_length);
  swString_append_ptr(response, buf, n);
  }
  //http cookies
  