Numerical Recipes License required for objective_sse_boxcox function

Hi @thober and @muellese. When working on MPR I wanted to update its dependency lightweight_fortran_lib. It is also used in mHM and there was another file added in August: mo_boxcox.f90. It uses some numerical recipes which do not come under LGPL as the rest of the code (see also issue #26 (closed)). The functions used are brent, mnbrak, swap, shft. How do we proceed there?