code: function(style, stylename)
  	{
  		if (mxUtils.indexOfStylename(style, stylename) < 0)
  		{
  			if (style == null)
  			{
  				style = '';
  			}
  			else if (style.length > 0 && style.charAt(style.length - 1) != ';')
  			{
  				style += ';';
  			}
  			
  			style += stylename;
  		}
  		
  		return style;
  	}
docs: Function: addStylename
  
  Adds the specified stylename to the given style if it does not already
  contain the stylename.