Specifically check for 192-bit option in std.random.XorshiftEngine.
Correct typo in Xorshift32 which was leading to non-uniform behaviour.

The original typo derives directly from George Marsaglia's paper
introducing the Xorshift RNGs.  The original checking values, derived
from that code, thus also reflect the typo.

A corrected version of the reference code is available from
https://github.com/WebDrake/xorshift/ and has been used to
generate the updated checking values.
Correct typo in Xorshift160 which was leading to non-uniform behaviour.

The original typo derives directly from George Marsaglia's paper
introducing the Xorshift RNGs.  The original checking values, derived
from that code, thus also reflect the typo.

A corrected version of the reference code is available from
https://github.com/WebDrake/xorshift/ and has been used to
generate the updated checking values.
Merge pull request #1403 from WebDrake/xorshift

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