/*
   * Add a selector as key/value pair
   *
   * NOTE:
   * the string value must be properly escaped (replace & with &, etc.)
   * in Ruby use CGI::escapeHTML()
   *
   * call-seq:
   *   options.add_selector "Key", "Value"
   *   options.add_selector "Key", end_point_reference
   *
   */
  void add_selector(VALUE k, VALUE v)