Man page edits

[solardiz]

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This is motivated by the criticism in https://www.openwall.com/lists/yescrypt/2024/03/21/1 that our wording "CPU time cost" was misleading, given that with memory-hard methods it also affects memory usage. That's addressed in the first commit here. The second commit is based on my proof-reading of the entire crypt.5.

Not yet changed here, but something we might also want to change, is renaming of the count parameter to cost. Perhaps not only in man pages, but also in code.

Edit: This also fixes #29

[solardiz]

This also fixes #29

[solardiz]

@vt-alt You might want to review my edits of the gost-yescrypt description here.

[vt-alt]

@solardiz LGTM

[solardiz]

@besser82 @zackw Can you please merge this PR? I see no reason not to. You may say that more changes are desired, but that's no reason not to merge the changes so far. Thanks!

[zackw]

I have not had time to look at these changes at all. Please be patient.