util: avoid using hashlib on Python < 2.5 (issue2278)
The following patch allows the use of python2.4 with a standalone
hashlib rather than assuming that python2.5 is in use when hashlib is
imported successfully.
.. Common link and substitution definitions.
.. |hg(1)| replace:: **hg**\ (1)
.. _hg(1): hg.1.html
.. |hgrc(5)| replace:: **hgrc**\ (5)
.. _hgrc(5): hgrc.5.html
.. |hgignore(5)| replace:: **hgignore**\ (5)
.. _hgignore(5): hgignore.5.html