bug#29551: 24.5; doc string of `bookmark-alist'

[Eli Zaretskii]

> Date: Sun, 3 Dec 2017 15:41:10 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> A bookmark is more than a name.
> 
> The first line of the doc string says this:
> 
>   Association list of bookmarks and their records.
> 
> That's wrong, or at best misleading.  Each entry in the alist is a
> _bookmark_.  That is, each entry is a bookmark "record", whose car
> is the bookmark name, and whose cdr is the associated bookmark data.
> 
> The doc should say something like this:
> 
> "Association list of bookmark names and bookmark data."
> or
> "Association list of bookmark records." (and then say what a record is)

Thanks, fixed.