backport montanaro's checkin of
    revision 1.24 of calendar.py

make _localized_name instances work more like the tuples they replaced.  In
particular, negative indexes work and they are limited by the actual length
of the names they represent (weekday and month names).  This closes bug
#503202.

[and then]

Corrected _localized_name.__getitem__ based on code in patch 503202 (which I
thought was just a bug report, so didn't notice - doh!).  This handles
slicing, which v 1.23 didn't.