We check if the string value is different than the casted int value,
if so it means that the integer is beyond PHP_INT_MAX or PHP_INT_MIN
and we simply return the string value. This is also useful on Windows
builds of PHP since the maximum integer size (prior to PHP 7.0) is 32
bits even for 64 bit builds.
This could be triggered when passing an array with "holes" to variadic commands.
Connection classes based on the protocol serialized exposed by phpiredis were
not affected by this bug.
Fixes#316.
Daniele Alessandri