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

Closes https://github.com/cython/cython/pull/4101
See https://github.com/cython/cython/issues/4100

* Handle constant folding for LanguageLevel 2 on Python 3. Ensure that when StrNode is a BytesLiteral, that we don't coerce it to unicode.
* Add test for string multiplication bug. Needed to change the TreePath slightly to allow bytes-to-str comparison.

Fixes https://github.com/cython/cython/issues/3951

Remove incorrect dict unpacking optimisation that leaked external dict changes into the result (GH-4091)

Closes https://github.com/cython/cython/issues/3227

Creating global CDEFS for holding compiler definitions. Then pass it to the distutils.

Also add .vscode folder to .gitignore

Fixes https://github.com/cython/cython/issues/4096

Remove incorrect dict unpacking optimisation that leaked external dict changes into the result (GH-4091)

Closes https://github.com/cython/cython/issues/3227

Closes https://github.com/cython/cython/issues/4113

Replace usage of the seemingly CPython-internal Py_ISSPACE() macro by a dedicated inline function to make it work in C++ (where Py_ISSPACE() fails to link).

Closes https://github.com/cython/cython/issues/4111
Closes https://github.com/cython/cython/pull/4112

* Handle constant folding for LanguageLevel 2 on Python 3. Ensure that when StrNode is a BytesLiteral, that we don't coerce it to unicode.
* Add test for string multiplication bug. Needed to change the TreePath slightly to allow bytes-to-str comparison.

Fixes https://github.com/cython/cython/issues/3951

Fix optimised_pow2_inplace() doctest on Python 3.10 because the error message changed.

Python 3.9 error message:
    unsupported operand type(s) for ** or pow(): 'int' and 'str'

Python 3.10 error message:
    unsupported operand type(s) for **=: 'int' and 'str'

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.