LoopControl switch from using rand() to using random() for its random numbers when exploring new tile sizes but kept using RAND_MAX to normalize the random number to the range [0,1).

It most likely makes no difference on Linux systems with glibc where (at least on my workstation) RAND_MAX is INT_MAX ie 2^31-1 which is the documented range for random.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2517/loopcontrol-uses-rand_max-as-the-range-for