Bug report: Phalcon\Cache\Backend\Xcache

It seems that delete/queryKeys method are not implemented.

1. $cache->delete won't work.
2. queryKeys throws exception: keys need to be enabled to use this function (options['statsKey'] == '_PHCM')!

Test: $frontend = new \Phalcon\Cache\Frontend\Data(array( "lifetime" => 3600 )); $cache = new \Phalcon\Cache\Backend\Xcache($frontend, array( 'prefix'=>'user-data' ));

$cache->save('key', 'value'); $cache->delete();//don't work; $cache->queryKeys();//throw execption