Message 80754 - Python tracker

Instead of tp_reserved, the name should be tp_deprecated_compare.

There should be a python-dev discussion around when to actually remove
the slot:

  3.0.1 -- binary incompatibility between minor releases (BAD)
  3.1.0 -- uncomfortable for writers who have to add #ifdefs
  4.0.0 -- no pain, just wasted space
  3.1.5 -- just plain mean :-)