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

[Heinz Rommerskirchen <heinz@h-rommerskirchen.de>]

dired-do-find-regexp can't find matches for a regexp containing newline.
To trigger the bug:
- start "emacs -Q"
- open "/usr/local/share/emacs/25.0.93/etc/" in dired
- mark the file NEWS and maybe a few more
- type "A C-q C-j C-q C-j"
- there is a message in the echo area: "No matches for:

"
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.

In GNU Emacs 25.0.93.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.16.7, 
cairo version 1.14.2)
  of 2016-04-28 built on canna
Windowing system distributor 'The X.Org Foundation', version 11.0.11702000
System Description:	openSUSE Leap 42.1 (x86_64)

Configured using:
  'configure --with-cairo --with-modules --with-xwidgets'

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO IMAGEMAGICK SOUND GPM DBUS GCONF
GSETTINGS NOTIFY GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES XWIDGETS

Important settings:
   value of $LC_COLLATE: C
   value of $LC_NUMERIC: C
   value of $LANG: de_DE.UTF-8
   value of $XMODIFIERS: @im=local
   locale-coding-system: utf-8-unix

Major mode: Dired by name

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   buffer-read-only: t
   line-number-mode: t
   transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
user-error: No matches for:
  [2 times]
Note: file is write protected
<C-f4> is undefined
user-error: No matches for:

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message format-spec rfc822 mml mml-sec
password-cache epg epg-config gnus-util mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util help-fns mail-prsvr mail-utils find-dired
semantic/fw mode-local find-func xref cl-seq project eieio byte-opt
bytecomp byte-compile cconv eieio-core cl-macs gv cl-extra help-mode
easymenu grep compile comint ansi-color ring dired-aux cl-loaddefs pcase
cl-lib dired time-date mule-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
elisp-mode lisp-mode prog-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
frame cl-generic cham georgian utf-8-lang misc-lang vietnamese tibetan
thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian
slovak czech european ethiopic indian cyrillic chinese charscript
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote dbusbind inotify
dynamic-setting system-font-setting font-render-setting xwidget-internal
cairo move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 110376 4867)
  (symbols 48 21765 0)
  (miscs 40 70 143)
  (strings 32 20598 4326)
  (string-bytes 1 649249)
  (vectors 16 14946)
  (vector-slots 8 464287 4193)
  (floats 8 225 154)
  (intervals 56 513 0)
  (buffers 976 14)
  (heap 1024 42366 1243))