bug#17569: 24.4.50; doc of "wrapper hooks"

[Stefan Monnier <monnier@iro.umontreal.ca>]

> wrapper hooks too. (Though in general I don't understand why you delete
> documentation of obsolete features, rather than simply adding a "The
> following refers to an obsolete feature. In new code, use FOO" or
> somesuch at the start.)

I don't think it's worth documenting that which we discourage.  But if
you want to document how to replace such code with the new feature,
that's fine.

> filter-buffer-substring-function, completion-in-region-function,
> abbrev-expand-function don't seem to be documented.

`completion-in-region-function' is probably not worth documenting.
But the filter-buffer-substring-functions and abbrev-expand-functions
documentation should be changed indeed to document
filter-buffer-substring-function and abbrev-expand-function instead.


        Stefan