Fix: resolve strict NOTICE when userland extends and overrides get() et al

In v2.2.0b1, any user-land class extending Memcached, and then overriding methods such as get(), would receive this strict NOTICE from PHP:

    PHP Strict standards:  Declaration of MyMemcached::get() should be compatible with Memcached::get($key, $cache_cb = NULL, $cas_token = NULL, $udf_flags = NULL) in /home/stuart/Devel/php-memcached-dev/included_memcached.php on line 9

I've traced this to a few cases where the first param to ZEND_ARG_INFO was '2'.  Changing these to '1' fixes this PHP strict NOTICE.