Avoid overflow when generating negative integers with PHP_MIN_INT as
boundary.

Signed integers goes from −9,223,372,036,854,775,808 to
9,223,372,036,854,775,807 on a 64 bits system.

The generator algorithm was doing this:

Context:
$upperLimit = 0;
$lowerLimit = −9,223,372,036,854,775,808;

rand(0, ($this->upperLimit - $this->lowerLimit));

which was causing a 0 + 9,223,372,036,854,775,808 which is a clear
overflow.