With python-2.6, importing the Crypto.Hash.MD5 and Crypto.Hash.SHA modules

With python-2.6, importing the Crypto.Hash.MD5 and Crypto.Hash.SHA modules
from pycrypto triggers warnings since those modules are implemented using
the deprecated md5 and sha modules from python's stdlib. So, in order to
avoid the warning and the inferior hash implementations that come with them,
never use these particular modules from pycrypto. Instead, use hashlib or
directly use stdlib's md5 and sha modules if necessary. Thanks to Markus
Peloquin for reporting.

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