Atlas analysis monitor dynamic branch hooks

i'll do it, but only because it makes you happy. :)
this seems like a place that can identify or cause headaches.  using a set does not allow us to control the order of the handlers, which may become important.  not tracking multiple adds of a given handler doesn't bother me because it is by definition "the same handler".
because this is all up-front costs, in your scenario we'd only do this 1000 times, resulting in basically <.01sec difference.