cpuminer-opt-3.16.1

New options for verthash:
--data-file to specify the name, and optionally the path, of the verthash
data file, default is "verthash.dat" in the current directory.
--verify to perform the data file integrity check at startup, default is
not to verify data file integrity.

Support for creation of default verthash data file if:

1. --data-file option is not used,
2. no default data file is found in the current directory, and,
3. --verify option is used.

More detailed logs related to verthash data file.

Small verthash performance improvement.

Fixed detection of corrupt stats caused by networking issues.