disable asyncio coroutine test in Py3.4(.3) due to an annoying type check: Py3.5 has a fix and later 3.4 versions might, too

Revert "make Coroutine type a non-iterable/iterator and instead let __await__() return a thin Iterator wrapper"

This reverts commit cf51fa4e.

make Coroutine type a non-iterable/iterator and instead let __await__() return a thin Iterator wrapper

make sure Cython's generator and coroutine types are registered with the Generator/Coroutine ABCs also in Py3.5
patch both types also into asyncio (in Py<3.5)

rewrite __Pyx_ReturnWithStopIteration() to fix returning tuples and also fix it on the other side in __Pyx_PyGen_FetchStopIterationValue()

make Cython's Coroutine type and extension types work with Python's async-for loop, implement new slots in Py3.5

* Add Python 2.6 x86/x64 to the build matrix.
* Use clone_depth option, no need to clone the full repo.
* Build master branch and last release branch.
* Use up-to-date pip and setuptools.
* Build wheels, msi, and wininst installers.

Use different mangling prefix in foo_api.h files

Fix links to CEP 516