posix: remove is-comparison between integers
Comparing integers by identity relies on a CPython implementation
detail of caching integers between -5 and 256.[1]
[1] <http://docs.python.org/c-api/int.html#PyInt_FromLong>
.. 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