tests: fuzz testing of multi_compress_to_buffer()
tests: fuzz testing of multi_compress_to_buffer()

It found a bug related to worker dispatching, which was fixed a few
commits ago.
terrelln/python-zstandard,terrelln/python-zstandard,terrelln/python-zstandard,indygreg/python-zstandard,indygreg/python-zstandard,indygreg/python-zstandard,terrelln/python-zstandard,indygreg/python-zstandard