A dict that preserves insertion order and otherwise resembles the
dict builtin (if it isn't it) rather than `collections.OrderedDict`.
Also:
* compat_builtins_dict: the built-in definition in case `compat_dict`
was imported as `dict`
* compat_dict_items: use instead of `dict.items` to get items from
a `compat_dict` in insertion order, if you didn't define `dict` as
`compat_dict`.