code: function (x, y, w, h, options) {
                      return SVGRenderer.prototype.symbols[
                        !defined(options) || !options.r ? 'square' : 'callout'
                        ].call(0, x, y, w, h, options);
                  }
docs: Add rectangle symbol path which eases rotation and omits arcsize problems
  compared to the built-in VML roundrect shape. When borders are not rounded,
  use the simpler square path, else use the callout path without the arrow.