Fixed ParseError in stub file (#468)

Match PHP 7 version of the file which has NULL as the default value of this bool argument.

Author: GrahamCampbell

Diff for: php_memcached.stub.php

@@ -17,8 +17,8 @@ public function get(string $key, callable $cache_cb=NULL, int $get_flags=0): mix
 	public function getByKey(string $server_key, string $key, callable $cache_cb=NULL, int $get_flags=0): mixed {}
 	public function getMulti(array $keys, int $get_flags=0): false|array {}
 	public function getMultiByKey(string $server_key, array $keys, int $get_flags=0): false|array {}
-	public function getDelayed(array $keys, bool $with_cas=0, callable $value_cb=NULL): bool {}
-	public function getDelayedByKey(string $server_key, array $keys, bool $with_cas=0, callable $value_cb=NULL): bool {}
+	public function getDelayed(array $keys, bool $with_cas=NULL, callable $value_cb=NULL): bool {}
+	public function getDelayedByKey(string $server_key, array $keys, bool $with_cas=NULL, callable $value_cb=NULL): bool {}
 	public function fetch(): false|array {}
 	public function fetchAll(): false|array {}