Message 184431 - Python tracker

Additionally, in macros Py_XINCREF and Py_XDECREF we've took an opportunity to increase readability by changing expression:
> if (item == NULL) ; else action(item);
to more natural inverted condition:
> if (item != NULL) action(item);

There is a chance that there may be a reason for this form of expression, so let me know if this is an issue.