bpo-38113: Update the Python-ast.c generator to PEP384 (gh-15957)

Summary: This mostly migrates Python-ast.c to PEP384 and removes all statics from the whole file. This modifies the generator itself that generates the Python-ast.c. It leaves in the usage of _PyObject_LookupAttr even though it's not fully PEP384 compatible (this could always be shimmed in by anyone who needs it).

Author: DinoV

Misc/NEWS.d/next/Core and Builtins/2019-09-11-14-10-02.bpo-38113.yZXC3P.rst

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+ast module updated to PEP-384 and all statics removed