Disable on macOS due to bug in Apple clang++. See https://github.com/cython/cython/pull/4448#issuecomment-964405071

* Initial support for Python 3.11 (GH-4414)

https://github.com/cython/cython/issues/4414

* Add a basic replacement for PyCode_New().

An optimized versions would be nice, but this is intended to work sufficiently to start testing. Also, CPython 3.11 might actually add a new C-API function to simplify setting the current code position. That might be used instead.

* Disable introspection of frame object with vectorcall

This feature looked to only be used for early Python versions that don't have the full vectorcall protocol (and the contents of the frame object are changed in Python 3.11).

* Use new C-API function to get the current frame on Python 3.11 alpha (GH-4427)

Use the accessor function instead of the direct struct member (which is now the wrong type).

https://github.com/cython/cython/issues/4427
Closes https://github.com/cython/cython/issues/4416

* Fix number of arguments

* Disable CYTHON_FAST_PYCALL for 3.11 in Cython 0.29.x due to non-trivial incompatibilities.

* Remove remanent of 3.8alpha/beta workaround for PyCode_New().

All the versions we currently test are new enough that the alias is no longer necessary.

The string comparison was reporting '11' < '4' (so OpenMP tests were being skipped on GCC 11)

Fixes https://github.com/cython/cython/issues/3647

Use newer test dependencies in Py3.6+. (Excluding 3.10 for now to give the projects a bit more time.)

Disable some plain Python (non Cython related) tests that fail in Py3.10 due to changed error messages.

Originally discussed here:
https://groups.google.com/g/cython-users/c/rU0_mt3Vgn0

The function `(cython-current-defun)` of `cython-mode.el` had some issues:

* ran into an endless loop
* for `cdef`s and `cpdef`s it picked the function type rather than the function name.
* did not properly handle nested functions

Closes https://github.com/cython/cython/issues/3218

Tests are disabled on macOS+clang (failing with Apple clang++ 12) but appear to work fine on gcc-11.

Use the accessor function instead of the direct struct member (which is now the wrong type).

Closes https://github.com/cython/cython/issues/4416

Make coverage.py handle "stringsource" better by making it clear that it is not a file name (GH-4440)

Having a code object with `co_filename` set to just "stringsource" (e.g. when using memory views or auto-pickling), causes coverage.py to think that "stringsource" is a relative path to an actual file. The convention is to wrap such fake paths with angle brackets, which coverage.py correctly recognizes.

You will recognize this as the following error, e.g. when running "coverage html":
    No source for code: '.../stringsource'.
    Aborting report output, consider using -i.

Replace a mutable default argument with a None default and check since it is not intended to be mutated (GH-4435)

Avoid "possible loss of data" warning in MSVC by adding redundant casts to code that gets discarded later.

Still requires the more conservative __index__ here rather than a possibly
truncating __int__ because this is used in a context where floating point
values should probably be treated specially.

This fixes Github issue #2752.

PyContextVar_Get() was added in PyPy 7.3.6.
https://foss.heptapod.net/pypy/pypy/-/blob/branch/default/pypy/doc/release-v7.3.6.rst

Some overloaded methods are commented out as they currently result in incorrect C++ code.
See https://github.com/cython/cython/pull/4423#issuecomment-953685310

Repair coverage tests to make them work with coverage 6.1, which changed the HTML output format that the tests parse.