suzerain: record derivative operator

Just burned way too long recovering this...

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42535 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: #2503 catalog \partial_y results

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@42536 0bd85f0b-c151-43b9-a1e9-27231104551f