The first change is to make sure we always define PY_SSIZE_T_CLEAN
before including Python.h. Starting from Python 3.10 this is required.
Otherwise we get errors like this:
SystemError: PY_SSIZE_T_CLEAN macro must be defined for '#' formats
The second change is to update reflection_test.py to account for the
fact that with Python 3.10, we get a TypeError even with the C++
implementation when trying to assign a float to a bool field. I'm not
sure why this changed with Python 3.10, but it seems like a good thing
since this is the desired behavior anyway.
