bug#23956: 25.1.50; Underscore display error in WoMan mode

[Meiyo Peng]

The underscore character "_" is displayed as a backslash and an
underscore "\_" in WoMan mode. Is this a bug or a feature?

This is from ~M-x woman docker-attach~:
#+BEGIN_EXAMPLE
  * \\ (two backward slashes)
  * \_ (underscore)
  * ^ (caret)
#+END_EXAMPLE

This is from ~M-x man docker-attach~:
#+BEGIN_EXAMPLE
  · \\ (two backward slashes)
  · _ (underscore)
  · ^ (caret)
#+END_EXAMPLE


------------------------------------------------------------

In GNU Emacs 25.1.50.2 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
of 2016-07-11 built on lgw01-13
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description: Ubuntu 16.04 LTS

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Building list of manual directory expansions...
Building completion list of all manual topics...
uncompressing docker-attach.1.gz...done
WoMan formatting buffer...done in 0.0142214 seconds
Making completion list...

Configured using:
'configure --build=x86_64-linux-gnu --prefix=/usr
'--includedir=${prefix}/include' '--mandir=${prefix}/share/man'
'--infodir=${prefix}/share/info' --sysconfdir=/etc --localstatedir=/var
--disable-silent-rules '--libdir=${prefix}/lib/x86_64-linux-gnu'
'--libexecdir=${prefix}/lib/x86_64-linux-gnu' --disable-maintainer-mode
--disable-dependency-tracking --prefix=/usr --sharedstatedir=/var/lib
--program-suffix=-snapshot --with-x=yes --with-x-toolkit=gtk3
'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
-Werror=format-security' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2'
'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

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

Important settings:
value of $LANG: en_US.UTF-8
value of $XMODIFIERS: @im=fcitx
locale-coding-system: utf-8-unix

Major mode: WoMan

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

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message puny seq byte-opt gv bytecomp
byte-compile cl-extra help-mode cconv dired dired-loaddefs format-spec
rfc822 mml mml-sec password-cache epa derived epg epg-config gnus-util
rmail rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils imenu disp-table view jka-compr woman man
easymenu cl-loaddefs pcase cl-lib ansi-color time-date mule-util tooltip
eldoc electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
term/x-win 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 term/tty-colors 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 obarray 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 move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 142064 5664)
(symbols 48 21630 0)
(miscs 40 655 168)
(strings 32 29670 5205)
(string-bytes 1 767432)
(vectors 16 14907)
(vector-slots 8 476002 4875)
(floats 8 189 28)
(intervals 56 575 0)
(buffers 976 14)
(heap 1024 20283 938))