Move module_invoke() into ModuleHandler

function module_invoke($module, $hook) {
  $args = func_get_args();
  // Remove $module and $hook from the arguments.
  unset($args[0], $args[1]);
  if (module_hook($module, $hook)) {
    return call_user_func_array($module . '_' . $hook, $args);
  }
}

  public function invoke($module, $hook, $args = array()) {
    if (!$this->implementsHook($module, $hook)) {
      return;
    }
    $function = $module . '_' . $hook;
    return call_user_func_array($function, $args);
  }

function module_hook($module, $hook) {
  $function = $module . '_' . $hook;
  if (function_exists($function)) {
    return TRUE;
  }
  // If the hook implementation does not exist, check whether it may live in an
  // optional include file registered via hook_hook_info().
  $hook_info = module_hook_info();
  if (isset($hook_info[$hook]['group'])) {
    module_load_include('inc', $module, $module . '.' . $hook_info[$hook]['group']);
    if (function_exists($function)) {
      return TRUE;
    }
  }
  return FALSE;
}

  public function implementsHook($module, $hook) {
    $function = $module . '_' . $hook;
    if (function_exists($function)) {
      return TRUE;
    }
    // If the hook implementation does not exist, check whether it lives in an
    // optional include file registered via hook_hook_info().
    $hook_info = $this->getHookInfo();
    if (isset($hook_info[$hook]['group'])) {
      $this->loadInclude($module, 'inc', $module . '.' . $hook_info[$hook]['group']);
      if (function_exists($function)) {
        return TRUE;
      }
    }
    return FALSE;
  }