Respond to a path being updated.
$path: An associative array containing the following keys:
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_path_update($path) {
db_update('mytable')
->fields(array(
'alias' => $path['alias'],
))
->condition('pid', $path['pid'])
->execute();
}