Add option to test runner to ensure determinism.
Add option to test runner to ensure determinism.

ChristopherHogan/cython,cython/cython,scoder/cython,cython/cython,da-woods/cython,ChristopherHogan/cython,scoder/cython,da-woods/cython,ChristopherHogan/cython,scoder/cython,da-woods/cython,scoder/cython,cython/cython,da-woods/cython,cython/cython