plt/racket — pull request #815 by stchang (2014-11-05 19:11:13+00:00)
Title: add identifier sets (in syntax/id-set)

Second attempt at adding identifier sets (some previous discussion here: https://github.com/plt/racket/pull/807).

If there are no complaints, I would like to merge. @rmculpepper and @carl-eastlund, would you mind taking a look if you have time?