[issue21233] Add *Calloc functions to CPython memory allocation API

[STINNER Victor]

STINNER Victor added the comment:

Changes on the pickle module don't look like an interesting optimization. It even looks slower.

$ python perf.py -b fastpickle,fastunpickle,pickle,pickle_dict,pickle_list,slowpickle,slowunpickle,unpickle ../default/python.orig ../default/python.calloc
...

Report on Linux selma 3.13.9-200.fc20.x86_64 #1 SMP Fri Apr 4 12:13:05 UTC 2014 x86_64 x86_64
Total CPU cores: 4

### fastpickle ###
Min: 0.364510 -> 0.374144: 1.03x slower
Avg: 0.367882 -> 0.377714: 1.03x slower
Significant (t=-11.54)
Stddev: 0.00493 -> 0.00347: 1.4209x smaller

The following not significant results are hidden, use -v to show them:
fastunpickle, pickle_dict, pickle_list.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21233>
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