bench methods implemented in C (yay!).

method calls and returns who originated from code implemented in C
receive what I think is the callers binding from set_trace_func.

we can work around the absence of self by matching against the method
name instead and then using the first event(call) and last event(return).
if we hit other methods with the same name along the way it shouldn't matter
since the first event and last event should always aligned for the method
being traced.