bug#23830: 25.0.94; Emacs eats left Windows key on Windows 7

[Richard Copley]

In recent builds of the emacs-25 branch, when an Emacs frame is in the
foreground, it intercepts the left Windows key (and the windowing
system does not react to the key event).

My two most recent emacs-25 builds are from revisions:
  ab182c624868fcc0ed97597db669911099d4bd28 (commit time 2016-06-12
17:33:52 UTC),
  788c9b69e1801dd883dbe603281571ef3c78a724 (commit time 2016-05-31
06:17:55 UTC).
The bug is present in the 2016-06-12 build and absent in the 2016-05-31 build.

To reproduce:

Run emacs -Q.
Make sure the Emacs frame is the active foreground window.
Press the left Windows key.
Expected result: the start menu opens (depends on users's settings).
Actual result: Emacs receives the keypress instead (this can be verified
by typing [C-h k lwindow]).

In GNU Emacs 25.1.50.1 (x86_64-w64-mingw32)
 of 2016-06-13 built on [redacted]
Repository revision: ab182c624868fcc0ed97597db669911099d4bd28
Windowing system distributor 'Microsoft Corp.', version 6.1.7601
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --prefix /C/emacs/emacs-20160612-173352 --enable-checking
 --with-modules --without-imagemagick --disable-dependency-tracking
 --enable-locallisppath=%emacs_dir%/../site-lisp 'CFLAGS=-Og -g -ggdb'
 CPPFLAGS=-D_WIN32_WINNT=_WIN32_WINNT_WIN7'

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

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

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 cl-loaddefs pcase cl-lib dired
dired-loaddefs format-spec rfc822 mml easymenu 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
time-date mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel dos-w32 ls-lisp disp-table term/w32-win 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 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 w32notify dbusbind w32 multi-tty
make-network-process emacs)

Memory information:
((conses 16 98764 8768)
 (symbols 56 20613 0)
 (miscs 48 41 87)
 (strings 32 18921 4980)
 (string-bytes 1 580024)
 (vectors 16 13363)
 (vector-slots 8 441864 3974)
 (floats 8 181 78)
 (intervals 56 253 11)
 (buffers 976 11))