bug#23426: 25.0.93; dired-do-find-regexp doesn't find newline

[Glenn Morris]

Dmitry Gutov wrote:

>> - type "A C-q C-j C-q C-j"
[...]
>> In former versions of Emacs (e.g. 24.5.1) this same recipe brought you
>> to the first empty line in one of the marked files.
>
> I don't know if it's possible to search for "A^J^J" using find+grep,
> and it's the implementation choice for this function.

(The fact that it uses grep should perhaps be documented, since it
affects what one can search for.)

For this specific example, a grep-ish way to find empty lines is '^$'.
However, using "A" to search for that (or the empty regexp) causes Emacs
to hang indefinitely. :(