Implements hook_TYPE_alter() on behalf of block module.
This is for verifying that drupal_alter(array(TYPE1, TYPE2), ...) allows hook_module_implements_alter() to affect the order in which module implementations are executed.
function block_drupal_alter_foo_alter(&$data, &$arg2 = NULL, &$arg3 = NULL) {
$data['foo'] .= ' block';
}