accept periodic solution in simulations ONLY IF two regimes differ by one...

accept periodic solution in simulations ONLY IF two regimes differ by one period, to avoid pathological solutions.

We also do not check for periodicity when check ahead periods have been increased endogenously, again to avoid mis-identified periodicity.

Any other type of periodicity, is flagged as non-convergence with error code 313 (infinite loop of solutions).

(cherry picked from commit d0150997)