Overlay modification-hooks no longer running after 564d811725 (under certain configurations)

[Mitchel Humpherys <mitch.special@gmail.com>]

Hello,

I noticed recently that iedit [1] stopped working on the emacs-25 and
master branches.  I finally got around to git bisect'ing it today and
found that the breaking commit is:

    commit 564d811725596f15ecf543777e11504b47d2af86
    Author: Eli Zaretskii <eliz@gnu.org>
    Date:   Fri Nov 6 17:19:39 2015 +0200
    
        Don't invoke overlay modification hooks in wrong buffer

The relevant iedit code seems to be:

    (overlay-put occurrence 'insert-in-front-hooks '(iedit-occurrence-update-hook))
    (overlay-put occurrence 'insert-behind-hooks '(iedit-occurrence-update-hook))
    (overlay-put occurrence 'modification-hooks '(iedit-occurrence-update-hook))

(from [2]).  If I revert the commit above on the emacs-25 tip (or
checkout that commit's parent), the hook does run and iedit works as
expected.

I apologize for not filing a bug, but I don't have an `emacs -Q' recipe,
so there must be some other interaction with my config going on, which I
haven't tracked down...  It's also possible that iedit is incorrectly
relying on some broken behavior.

I was hoping someone might have an idea of what's going on here.  If
not, I'll continue pursuing a smaller repro recipe.

[1] https://github.com/victorhge/iedit
[2] https://github.com/victorhge/iedit/blob/master/iedit-lib.el#L287

-- 
Mitch