Add relocatable Linux install

pyatomic: fix warning on MSVC

The __has_builtin(__atomic_load) check has to be nested with the clang
check or MSVC will issue a warning, which breaks the NumPy Windows
build.

Update pythonba.vcxproj from upstream CPython

This fixes the Windows GitHub actions build

Add "nogil" identifier to Py_GetVersion()

Python 3.11.0a1

Python 3.10.0

Python 3.10.0rc2

Python 3.7.12

Python 3.6.15

Python 3.9.7