Prepare Stacklss 3.5 #112

Description
Originally reported by: Anselm Kruis (Bitbucket: akruis, GitHub: akruis)
Python 3.5 adds a few new features, which affect Stackless. Here are the results of a quick and dirty review of What’s New In Python 3.5:
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https://bugs.python.org/issue21205: New generator attribute __qualname__. PyGenObject gets two new members: gi_name and gi_qualname.
Pickling support implemented: a8f3bfa783a9
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https://bugs.python.org/issue19235: new RecursionError exception
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https://bugs.python.org/issue24400: PEP 492 - Coroutines with async and await syntax
As part of the PEP 492 implementation, the tp_reserved slot of PyTypeObject was replaced with a tp_as_async slot. Refer to Coroutine Objects for new types, structures and functions.
The coroutine type is just a variant of the generator type. Therefore it is possible to reuse the pickling code for generators to enable pickling of coroutines. Implemented with commit e2bf67837ac2.