Dynare++: fix check for QZ eigenvalue criterium

The criterium was previously incorrectly applied to the square absolute value
of eigenvalues. Rather apply it to the absolute value itself (as now done in
Dynare).

Ref #1632

dynare++/kord/first_order.cc

@@ -14,7 +14,7 @@ double qz_criterium = 1.000001;
 lapack_int
 order_eigs(const double *alphar, const double *alphai, const double *beta)
 {
-  return (*alphar **alphar + *alphai **alphai < *beta **beta * qz_criterium);
+  return (*alphar **alphar + *alphai **alphai < *beta **beta * qz_criterium * qz_criterium);
 }
 
 /* Here we solve the linear approximation. The result are the matrices