python-cython C++ support patch

[Masamichi Hosoda]

>> PyMODINIT_FUNC unfortunately dos not work and my changes try
>> to overcome it, see similar on
>> 
>> https://sourceware.org/pipermail/cygwin/2021-January/247211.html
>> 
>> but your portion is for additional C++ case
>> than I am adding in asimilar way
>> 
>> Regards
>> Marco
>
> a test package has been just uploaded.
> Try it and tell me if it solves your problem.
>
> Otherwise point me to your C++ code and I will look on it.
>
> Regards
> Marco

python38-cython-0.29.21-3 works fine with following test code.

```hello.pyx
print('Hello World!')
```

```setup.py
from distutils.core import setup
from Cython.Build import cythonize

setup(
    ext_modules=cythonize(
        "hello.pyx",
        language="c++",
    )
)
```

```test.py
import hello
```

Here's the result by python38-cython-0.29.21-2 (failed).

```
$ python setup.py build_ext --inplace
[...snip...]
$ python test.py
Traceback (most recent call last):
  File "test.py", line 1, in <module>
    import hello
ImportError: dynamic module does not define module export function (PyInit_hello)
```

Here's the result by python38-cython-0.29.21-3 (succeeded).

```
$ python setup.py build_ext --inplace
[...snip...]
$ python test.py
Hello World!
```

Thanks.