directly call $module_hook _lookup_path instead of module_hook

[hefox]

module_hook adds excessive function_exists

[hefox]

Don't know how patch workflow works on github :-/

--- a/includes/path.inc
+++ b/includes/path.inc
@@ -57,7 +57,8 @@ function drupal_lookup_path($action, $path = '', $path_language = '') {
}

if ($hook_module !== FALSE) {

• $retval = module_invoke($hook_module, 'lookup_path', $action, $path, $path_language);
• $function = $hook_module . '_lookup_path';
• $retval = $function($action, $path, $path_language);
  } else {
  $retval = _drupal_lookup_path_direct($action, $path, $path_language);
  }