cffi: don't process pool.h
cffi: don't process pool.h

We don't use any functions from it. No need to process it.
indygreg/python-zstandard,terrelln/python-zstandard,terrelln/python-zstandard,terrelln/python-zstandard,terrelln/python-zstandard,indygreg/python-zstandard,indygreg/python-zstandard,indygreg/python-zstandard