My C11 SHA256 implementation.
See `tests.c` for usage.
Benchmarks========== > time -p ./sha256 ~/Videos/8x*avi > /dev/null
rleal 9.39
user 9.10
sys 0.29
> time -p sha256sum ~/Videos/8x*avi > /dev/null
real 12.04
user 11.73
sys 0.31
> time -p openssl sha256 ~/Videos/8x*avi > /dev/null
real 6.36
user 6.01
sys 0.32