Act on a field instance being updated.
This hook is invoked from field_update_instance() after the instance record is saved, so it cannot be used by a module to modify the instance itself.
$instance: The instance as it is post-update.
$prior_instance: The instance as it was pre-update.
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_field_update_instance($instance, $prior_instance) {
// @todo Needs function body.
}