pep-492: Update benchmark code

Since coroutines now have a distinct type, they do not support
iteration. Instead of doing 'list(o)', we now do 'o.send(None)'
until StopIteration.

Note, that the updated timings are due to the difference of
doing a loop in Python vs doing it in C ('list()' vs 'while True').

pep-0492.txt

@@ -1310,21 +1310,29 @@ difference between "async" functions and generators::
         r = await abinary(n - 1)
         return l + 1 + r
 
-    def timeit(gen, depth, repeat):
+    def timeit(func, depth, repeat):
         t0 = time.time()
         for _ in range(repeat):
-            list(gen(depth))
+            o = func(depth)
+            try:
+                while True:
+                    o.send(None)
+            except StopIteration:
+                pass
         t1 = time.time()
         print('{}({}) * {}: total {:.3f}s'.format(
-            gen.__name__, depth, repeat, t1-t0))
+            func.__name__, depth, repeat, t1-t0))
 
-The result is that there is no observable performance difference.
-Minimum timing of 3 runs
+The result is that there is no observable performance difference::
 
-::
+    binary(19) * 30: total 53.321s
+    abinary(19) * 30: total 55.073s
 
-    abinary(19) * 30: total 12.985s
-    binary(19) * 30: total 12.953s
+    binary(19) * 30: total 53.361s
+    abinary(19) * 30: total 51.360s
+
+    binary(19) * 30: total 49.438s
+    abinary(19) * 30: total 51.047s
 
 Note that depth of 19 means 1,048,575 calls.