I could not find the original specification of this standard, although
many proprietary implementations exist (or claim to exist). Also there
are many 3rd-party descriptions of the method, which often differ in one
or another detail, but after some reading I could conclude that the most
likely definition should be as follows:
1. Fill the device with zeroes, do not verify.
2. Fill the device with ones, do not verify.
3. Fill the device with a PRNG stream, do verify.
In other words, this is a simplified version of nwipe's "dodshort".
Both display_help() and nwipe_options_parse() are consistent about the
--noblank option, in that it exists and has no short form. Make the man
page and nwipe_gui_noblank() indicate that correctly. Mention that "ops2"
never blanks the device regardless of the option.
