subtle dead code in prop/fav stuff
subtle dead code in prop/fav stuff

Summary:
A list of free variables was computed and passed around, but never used. The
reason OCaml wasn't complaining is that the list is eventually passed to a
recursive function, which passes it to its  recursive call, so it looks like
it's used there.

Reviewed By: mbouaziz

Differential Revision: D7098556

fbshipit-source-id: b22a591

facebook/infer,facebook/infer,facebook/infer,jvillard/infer,jvillard/infer,facebook/infer,jvillard/infer,jvillard/infer,jvillard/infer,jvillard/infer,facebook/infer,facebook/infer,jvillard/infer,facebook/infer