ssh-issue: replace verb options by normal verbs

ssh-issue: replace verb options by normal verbs

The interface of this program was rather strange. It took an option that
specified what to do, but that option behaved exactly like a verb. Let's
change the interface to the more modern style with verbs. Since the
inteface was documented in the man page, provide a compat shim to handle
the old options.

(In practice, I doubt anybody will notice the change. But since it was
documented, it's easier to provide the compat then to think too much
whether it is actually needed. I think we can drop it an year or so.)