After seeing set_size and thinking it redundant (thought it returned the
capacity of the set until I checked), I realized set_count would be a
much better name (set_count (node->successors) in qfcc does make much
more sense).
I never liked that some of the macros needed the type as a parameter
(yay typeof and __auto_type) or those that returned a value hid the
return statement so they couldn't be used in assignments.
