Fix issue raised by PHP 8.1

[remicollet]

1st commit fix bad param count raising funny message

Fatal error: Uncaught TypeError: Memcached::setMulti(): Argument #2 ($expiration) **must be of type int, int given** in /work/GIT/pecl-and-ext/memcached/tests/cas_multi.php:14````

2nd hides deprecation warning

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Using php 8.1.0 alpha1

=====================================================================
Number of tests :   95                81
Tests skipped   :   14 ( 14.7%) --------
Tests warned    :    0 (  0.0%) (  0.0%)
Tests failed    :    0 (  0.0%) (  0.0%)
Tests passed    :   81 ( 85.3%) (100.0%)
---------------------------------------------------------------------
Time taken      :   13 seconds
=====================================================================