bug#25825: 25.1; ispell-find-hunspell-dictionaries not working on Windows

[S W <sw9@outlook.com>]

I am using hunspell 1.3.2 on Windows from ezwinports.
ispell-find-hunspell-dictionaries isn't setting
ispell-hunspell-dictionary-alist properly because I believe LANG=ENU
is overriding the default dictionary. This results in "Can't open
affix or dictionary files for dictionary named \"ENU\" appearing in
hunspell-found-dicts instead of "default.aff", which results in
hunspell-default-dict being set to nil and an error when
ispell-parse-hunspell-affix-file(hunspell-default-dict) is called.

To reproduce in emacs -q
(setq ispell-program-name "path_to_hunspell")
M-x ispell-buffer

In GNU Emacs 25.1.1 (x86_64-w64-mingw32)
 of 2016-11-15 built on LAPHROAIG
Windowing system distributor 'Microsoft Corp.', version 10.0.14393
Configured using:
 'configure --without-dbus --without-compress-install 'CFLAGS=-O2
 -static -g3''

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

Important settings:
  value of $LANG: ENU
  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.
split-string: Wrong type argument: stringp, nil

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message idna dired 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 help-mode easymenu
cl-loaddefs pcase cl-lib mail-prsvr mail-utils ispell 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 w32 multi-tty make-network-process emacs)

Memory information:
((conses 16 91762 3533)
 (symbols 56 20003 0)
 (miscs 48 91 84)
 (strings 32 17048 5055)
 (string-bytes 1 472329)
 (vectors 16 11965)
 (vector-slots 8 427043 5530)
 (floats 8 160 19)
 (intervals 56 284 37)
 (buffers 976 23))