Allow requesting derivatives of dynamic model at command line

The manual states:

output=second|third
Instructs the preprocessor to output derivatives of the dynamic model at least up to the given
order

However, the attached mod-file does not run despite containing

//--+ options: output=third, stochastic +--.

due to

The derivatives were not computed for the required order. Make sure that you used the right order option inside the `stoch_simul' command
Error using print_info
k_order_pert was unable to compute the solution

example3.mod