The macro was introduced in #12724.

Fix closes Issue10087 -  fixing the output of calendar display in the html format. Patch by Chris Lambacher. Test Contributed by catherine.

Read from NULL raises SIGILL, not SIGSEGV, on Mac OS X Lion.

Confirm that the prime example is actually correct.  We get so many complaints about a "buggy example" on docs@python, let us hope this cuts them in half at least.

- Move a test from call time to define time
- Add the function name to __all__
- Improve docstring and docs

A few lines are now duplicated (named tuple definition and docstring)
but I think the end result reads better.