Fix Py_XDECREF

[dalcinl]

After the changes in #164, listing Py_XDECREF as an allowed symbol is no longer necessary. Py_XDECREF is static inline and if a symbol is produced (depending on C compiler optimization), it is a local symbol.

With this PR, the current list of allowed symbols becomes empty. I was not sure whether to remove it or keep it in case it is needed in the future. I sided for the second option and added a test (using some monkeypatching, hope that's OK). If you guys feel otherwise, then I can drop the last commit and push a new one removing the _ALLOWED_SYMBOLS list.

cc @isuruf for viz as the author of #164

[woodruffw]

Thanks @dalcinl! Sorry for the delayed response.

With this PR, the current list of allowed symbols becomes empty. I was not sure whether to remove it or keep it in case it is needed in the future. I sided for the second option and added a test (using some monkeypatching, hope that's OK). If you guys feel otherwise, then I can drop the last commit and push a new one removing the _ALLOWED_SYMBOLS list.

Yeah, let's just remove the constant entirely -- I think that's cleaner than monkey patching here 🙂

[dalcinl]

@woodruffw I've updated the PR accordingly. I still used a separate commit for the removal of _ALLOWED_SYMBOLS, just in case this thing is ever needed again in the future, then git revert can easily reinstate the thing.

[woodruffw]

Thanks!