suzerain: #2503 radial_nozzle.c in line w/ Octave

This gets me back to the situation where the Octave-based solver
and the GSL-based C code agree about answers.  From here I can
add the residual based testing I started late last week.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42689 0bd85f0b-c151-43b9-a1e9-27231104551f