aux_equations may diverge from those in the main model

aux_equations only contain the definition of auxiliary variables, and
may diverge from those in the main model (equations), if other model
transformations applied subsequently. This is not a problem, since
aux_equations is only used for regenerating the values of auxiliaries
given the others.

For example, such a divergence appears when there is an expectation
operator in a ramsey model, see
tests/optimal_policy/nk_ramsey_expectation.mod */