Fix Issue 10550 - Xorshift32 and Xorshift160 do not generate uniformly-distributed random numbers

Corrects a number of apparent typos in George Marsaglia's original paper describing Xorshift RNGs, which result in severe deviations from uniformity in the random variates generated by Xorshift32 and Xorshift160.

The uniformity of the random variates produced has been verified casually but not yet systematically (e.g. with a high-quality random number test suite such as dieharder or TestU01).

The updated checking values have been generated from a corrected copy of Marsiglia's reference code, available from https://github.com/WebDrake/xorshift