CollInt: Do not set IPOPT option jac_c_constant based on DAE linearity
The current line is
options[solver]['jac_c_constant'] = 'yes' if self.linear_collocation else 'no'
We are however assuming with that that any equality constraints added by the user are also linear, which is not guaranteed to be the case. I am not sure what happens when a user uses GoalProgrammingMixin, has fixed_minimize_variable
set, and has a second order minimization goal. One can argue that typically not many goals follow a minimizationgoal, but this is just one scenario wherein the option we add is not congruent with the problem formulation as done by the user.
Somewhat related to #1096 (closed), in that one might be lucky that the linearity check fails and this option is not set.
Edited by Tjerk Vreeken