cpuminer-opt-3.18.2

Issue #342, fixed Groestl AES on Windows, broken in v3.18.0.

AVX512 for sha256d.

SSE42 and AVX may now be displayed as mining features at startup.
This is hard coded for each algo, and is only implemented for scrypt
at this time as it is the only algo with significant performance differences
with those features.

Fixed an issue where a high hashrate algo could cause excessive invalid hash
rate log reports when starting up in benchmark mode.