Issue #21709: Fix the logging module to not depend upon __file__ being set

Issue #21709: Fix the logging module to not depend upon __file__ being set
properly to get the filename of its caller from the stack.  This allows it
to work if run in a frozen or embedded environment where the module's
.__file__ attribute does not match its code object's .co_filename.

This same much simpler always correct approach has already been deployed and
used widely in Python 3.4 per the issue referenced above.