check_options possible invalid options combination

[talassio]

Need to make sure regularization_solve is NOT called with opt%reg_order /= 2. We should catch the specific combination of options that triggers this "not yet supported" combination before entering the solver, at the check_options() phase.

This can be difficult, given that the regularization parameter can be changed dynamically internally, and this can change between steps (although only if a regularization parameter less than zero was sent in the first call). i.e., it's the value of this in the workspace that's important.

The checking of options opt%type_of_method==2 .And. opt%nlls_method==3 are certainly required.