bug#2514: 23.0.91; Obsolete variable pre-abbrev-expand-hook in manual

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Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

,----[ (info "(emacs)Expanding Abbrevs") ]
|    Expanding any abbrev first runs the hook `pre-abbrev-expand-hook'
| (*note Hooks::).
`----

However,

,----[ C-h v pre-abbrev-expand-hook RET ]
| pre-abbrev-expand-hook is a variable defined in `abbrev.el'.
| Its value is nil
| 
|   This variable is obsolete since 23.1;
|   use `abbrev-expand-functions' instead.
| 
| Documentation:
| Function or functions to be called before abbrev expansion is done.
| This is the first thing that `expand-abbrev' does, and so this may
| change
| the current abbrev table before abbrev lookup happens.
| 
| You can customize this variable.
| 
| [back]
`----