bug#10550: 24.0.92; doc of `history-length'

[Chong Yidong]

"Drew Adams" <drew.adams@oracle.com> writes:

> As far as the doc goes, the most important thing is missing.  One can
> pretty much guess that this value limits the length of history lists,
> but the question is which history-list entries are dropped: the oldest
> or the new ones?  Does the list stay the same, with new values rejected,
> or do new ones replace the oldest ones? Or do new ones replace the
> next-newest ones?  Why make users guess or experiment?
>
> And for the doc string the info is also missing about which history
> lists are affected: "those that don't specify their own maximum lengths"
> (to quote the Elisp manual).

OK, I edited it to make it extra super double plus obvious.