bug#30823: 25.3; modification-hooks of overlays are not run in some cases

[Eli Zaretskii]

> From: Ren Victor <victorhge@gmail.com>
> Date: Thu, 15 Mar 2018 12:15:57 +0800
> 
> Two factors：
> 
>    1.  A commit of Emacs， modification-hooks might not be run in some cases:
>     
> http://git.savannah.gnu.org/cgit/emacs.git/commit/src?id=564d811725596f15ecf543777e11504b47d2af86
> 
>    2.  In ggtags, an overlay is deleted in the overlay's modification-hooks:
>     
> https://github.com/leoliu/ggtags/blob/eec392d2d639030c5a51bce8431f2815ad8e7bc5/ggtags.el#L2306
> 
> Deleted overlay ceases to be attached to the buffer. If the buffer of
> the first overlay in the saved array doesn't match the current buffer,
> then all the modification hooks will not be run in this buffer.
> 
> Thus modes that depends on modification-hooks won't work together with
> ggtags-highlight-tag mode.
> 
> I think Emacs should support `delete-overlay' in modificaiton-hooks of
> overlays, like ggtags.  So I report this bug.

Thanks.  Can you provide a recipe starting from "emacs -Q" to
reproduce the problem?