non-negative least squares

[John Regehr]

I'm interested in creating a non-negative least squares routine in GSL
that has an interface similar to gsl_multifit_linear.  There appear to be
unencumbered NNLS codes in C available for downloading so I assume that
getting this working in GSL is mostly a matter of translating the matrix
access idioms into GSL calls?

I haven't hacked GSL before; does anyone have any advice for the best
place to put this, which GSL internals should be reused, etc?

Thanks,

John Regehr