bug#22436: read-coding-system uses wrong default when called from write-file

[Richard Copley]

>From "emacs -Q", enter a ‘ in the scratch buffer (e.g., by typing "C-x
8 ["). Save or write the buffer. The minibuffer prompts "Select coding
system (default chinese-iso-8bit): ".

In GNU Emacs 25.0.50.1 (x86_64-w64-mingw32)
 of 2016-01-22 built on MACHINE
Repository revision: f7dc6d8b5bb318e02a4016d93f8b34de0716f4dc
Windowing system distributor 'Microsoft Corp.', version 10.0.10586
Configured using:
 'configure --prefix /c/emacs/emacs-20160122-175552
 --without-imagemagick --disable-dependency-tracking
 --enable-locallisppath=%emacs_dir%/../site-lisp 'CFLAGS=-Og -g -ggdb''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS

Important settings:
  value of $LANG: ENG
  locale-coding-system: cp1252

Major mode: Lisp Interaction

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
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Saving file c:/temp/xyzzy...
Quit

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec 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 help-mode
easymenu cl-loaddefs pcase cl-lib iso-transl time-date mule-util tooltip
eldoc electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
dos-w32 ls-lisp disp-table w32-win w32-vars term/common-win 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 w32notify dbusbind w32
multi-tty make-network-process emacs)

Memory information:
((conses 16 91651 6242)
 (symbols 56 19640 0)
 (miscs 48 37 107)
 (strings 32 16064 5326)
 (string-bytes 1 434641)
 (vectors 16 15778)
 (vector-slots 8 819512 106167)
 (floats 8 162 20)
 (intervals 56 349 42)
 (buffers 976 12))