pylibfdt fails to work with 3.10

[rossburton]

ERROR: testCreate (__main__.PyLibfdtSwTests)
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SystemError: PY_SSIZE_T_CLEAN macro must be defined for '#' formats

PY_SSIZE_T_CLEAN is now mandatory in 3.10, so the module needs to define that symbol and change the length type from int to ssize_t in all # formats passed to eg Py_BuildValue.

I'm new to Swig so trying to figure out how to make this actually happen...

[rossburton]

So Python expects the length, or *arg4 in the %typemap(out) (const void *) typemap, to be Py_ssize_t. The API uses int so it needs to be cast.

[rossburton]

Made it work. Define PY_SSIZE_T_CLEAN, cast the ints to Py_ssize_t. Patch incoming once I've cleared it internally.

[dgibson]

Thanks for your patch, that's merged now, so I'm closing.