Issue #17728: Specify default precision for float.format for presentation types e, f, and g.
#13510: clarify that f.readlines() is note necessary to iterate over a file.  Patch by Dan Riti.
Issue #17703: Fix a regression where an illegal use of Py_DECREF() after interpreter finalization can cause a crash.
Issue #17710: Fix cPickle raising a SystemError on bogus input.