Feature request: Pass/fail test for ran_unif

[hkershaw-brown]

Use case

Recently we had a problem with perturb from single instance using the cce compiler (cce/15.0.1): #495
Digging into the problem we found that the ran_unif was not giving the expected results.
Our current random_sequence tests require a human to look at the output for 'correct' answers. It would be better to have a pass/fail test we can automate.

Is your feature request related to a problem?

yes see #495

Describe your preferred solution

ran_unif is using Mersenne Twister.
Run ran_unif with a known seed, compare the integers produced against a reference solution for the Mersenne Twister

Describe any alternatives you have considered

You could test the boz constants (see #495 boz_dart.f90) without needing to compile any dart code.
However, this won't catch other problems with the random number generator.