Re-disable third-party integration testing in Py2.6 entirely since most packages aren't compatible anymore (and I don't want to dig up the versions that are).

Freeze the test dependency packages for Python 2.x to prevent further deprecations. More and more packages drop Py2 support these days.

Only #define PY_SSIZE_T_CLEAN if it is not already #defined

Signed-off-by: Andrew V. Jones <andrew.jones@vector.com>

* Reject invalid underscore placements in float parser.
* Add a proper nan/inf float parser to prevent underscore-mixes like "in_f" from passing through.

Make a helper function in a C++ test correctly propagate exceptions so that it won't have to spit out compiler warnings.

Special case float parsing in PyPy since byte string access is likely slower there than a plain float object creation. (And it works in all PyPy versions.)

* DOC: make some github issues into links, doc fixes
* add a doc-requirements.txt for building docs
* use ':issue:' domains for github issues

Fixes https://github.com/cython/cython/issues/3537

Both the C code and the tests are largely copied from CPython.

Note that this currently only applies to Python classes, not to cdef classes. Maybe it could be applied to the second+subsequent bases but I don't think it's needed for the initial implementation.

Freeze the test dependency packages for Python 2.7 to prevent further deprecations. More and more packages drop Py2 support these days.

Fix include file: "pytime.h" is actually included by "Python.h" and should not get included directly.

Fix MSVC: Add an explicit warning to modules that use the "array.array" internals and try to compile in PyPy.
Closes https://github.com/cython/cython/issues/3448

The __self__ argument should be present only for bound functions.
Fixes https://github.com/cython/cython/issues/4036

Currently it isn't easily possible to get this working absolutely correctly for fused functions. I raise an attribute error but hasattr still returns True.

Additionally, Python 2 methods always have a __self__ attribute but set it to None. I follow Python 3 behaviour and don't have the attribute.

Closes https://github.com/cython/cython/issues/3448

Remove GNU specific "tm" struct fields "tm_zone" and "tm_gmtoff" from libc/time.pxd because they get in the way of automatic struct conversions.
See https://github.com/cython/cython/issues/3733

See https://github.com/cython/cython/issues/3919

The loop parameter of asyncio.sleep(), deprecated in Python 3.8, has
been removed in Python 3.10. asyncio.sleep() gets implicitly the loop
in Python 3.10 and it is safe to do the same on Python 3.6:
https://docs.python.org/dev/whatsnew/3.10.html#changes-in-the-python-api