Add support for Pyston 2.3.1

[undingen]

This commit integrates Pyston into manylinux. While Pyston 2.x is based on CPython 3.8 it's not ABI compatible so recompiling of binary extensions is required. Providing precompiled pip installable packages would greatly help our users.

• Pyston currently only runs on x86_64
• gets installed into /opt/python/pyston38-pyston_23_x86_64_linux_gnu -> /opt/_internal/pyston3.8-2.3.1
• manylinux2014 & manylinux_2_24 supported
• EOL manylinux2010 isn't supported because the supplied glibc is too old for Pyston
• musllinux is not supported

With this changes and the my WIP changes to cibuildwheel I was able to generate wheels for Pyston.

Notes:

• Please very carefully review my PR because this is the first time I'm working with manylinux.
• Patch is mainly copied from the script for PyPy.
• We don't have a PEP425 Python Tag yet.
• Compiling Pyston is not really feasible because it takes many hours and is only supported on Ubuntu and has quite a few additional dependencies that's why I'm using the binary package.

[undingen]

I have started modifying wheel to return pt38-pt23 for print("{0}-{1}".format(tag.interpreter, tag.abi)) in order to change the install location to /opt/python/pt38-pt23. https://github.com/undingen/wheel/tree/pyston_2.3.1

I guess it makes sense to first try to get the shortcut pt for pyston accepted and only than add Pyston to pypa. What do you folks think?

[mayeut]

too old, closing.