[cleanup] print a FutureWarning for deprecated tools
[cleanup] print a FutureWarning for deprecated tools

- print a FutureWarning for tools.Counter, tools.OrderedDict which should
  be replaced by the corresponding collections classes
- print a FutureWarning for tools.count which should be replaced by
  itertools.count
- print a FutureWarning for ContextManagerWrapper which should be replaced
  by other contextlib classes and functions

All of them where introduced for Python 2.6 and releases prior than 2.7.2
which where dropped more than 4 years ago. This stuff should be removed
soon.

Change-Id: Ibb80f6a5a7c2ca01cb765ff8075b7d02ec18553a

wikimedia/pywikibot-core,wikimedia/pywikibot-core