The problem was that we collected all annotations we knew about once when the
simplifier started and threaded them through the CoreM monad. If new interface
files were loaded during simplification, their annotations would not be
visible to the simplifier.

Now, we rebuild the annotation list at the start of every simplifier pass that
needs it (which is only SpecConstr at the moment). This ensures that we see
all annotations that have been loaded so far. This is somewhat similar to how
RULES are handled.