OrderedDict.copy() returns an OrderedDict

[gvanrossum]

We should add this to the stub for OrderedDict. (Both Python 2 and 3.)

Note that we can't fix this by using a self-type for dict.copy() because in general if you subclass dict and don't override copy(), your copy() method will return just a dict. But OrderedDict.copy() overrides this behavior and the typeshed stub should say so.

[elazarg]

I don't think this is closed yet. #1656 didn't fix this, since the added __copy__ method is related to the copy() protocol, not to the interface of OrderedDict. The right fix is to add a copy method (perhaps in addition to __copy__).

[ilevkivskyi]

Fixed by #1856