bug#22043: 25.0.50; search-forward and char folding

[Mike Kupfer <m.kupfer@acm.org>]

(Resending because I had some odd mailer behavior when I first tried to
send this.)

The "Lax Search" Info node says

    Searches in Emacs by default perform character folding

But I don't see search-forward or search-backward doing that.  For
example, in the scratch buffer of "emacs -Q" if I do

  ä C-p
  M-x search-forward RET a RET

Emacs complains that the search failed.  (If it matters, the "ä" was
input using the 3-key sequence COMPOSE " a .)

I suspect that this is a bug in the code.  If not, the Info text should
be more precise about what searches perform character folding by
default.

Also, assuming that this is a bug in the code, the doc strings for
search-forward and search-backward should mention
search-default-regexp-mode, just like they mention case-fold-search.


In GNU Emacs 25.0.50.2 (x86_64-unknown-linux-gnu, X toolkit, Xaw scroll bars)
 of 2015-11-28
Repository revision: ea087151a901da36dd9ddc0843583906afafc7c5
Windowing system distributor 'The X.Org Foundation', version 11.0.11604000
System Description:	Debian GNU/Linux 8.2 (jessie)

Configured using:
 'configure --prefix=/usr/new'

Configured features:
XPM JPEG TIFF GIF PNG SOUND NOTIFY LIBXML2 FREETYPE XFT ZLIB
TOOLKIT_SCROLL_BARS LUCID X11

Important settings:
  value of $LC_TIME: C
  value of $LANG: en_US.utf8
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  delete-selection-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  transient-mark-mode: t

Recent messages:
Loading vc...done
For information about GNU Emacs and the GNU system, type M-H C-a.
Deleting...done
(No files need saving)
Deleting...done
Creating customization items...
Creating customization items ...done
Resetting customization items...done
Creating customization setup...done
Mark saved where search started

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
mml-sec 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 misearch multi-isearch crm thingatpt
cus-edit cus-start cus-load wid-edit dired-x seq byte-opt gv bytecomp
byte-compile cconv cl-extra help-mode warnings server noutline outline
easy-mmode comint ansi-color ring xcscope easymenu advice ispell delsel
vc cl-loaddefs pcase cl-lib vc-dispatcher dired timeclock mdk-hacks
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 inotify dynamic-setting
font-render-setting x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 135420 7234)
 (symbols 48 24675 0)
 (miscs 40 479 429)
 (strings 32 27659 5728)
 (string-bytes 1 732934)
 (vectors 16 14940)
 (vector-slots 8 461430 6321)
 (floats 8 189 22)
 (intervals 56 392 11)
 (buffers 976 16)
 (heap 1024 44618 759))