Changed the example to show how to create types the new way:
- Use a class new method rather than a new function.
- Use self->ob_type->tp_free in deallocators
- Use attribute descriptors rather than set/getattr methods.
- Make the type usable as a base type.
I split the example into 3 parts:
1. The minimal new type
2. Adding attributes and methods.
3. Finer control over attributes.
It's much simpler to define builtin types. These updates hopefully
show this.
I also made minor wording changes in two other places.
I still need to update xxobject.c