bug#18894: 24.4.51; Erratic freezing on Cygwin

[aidalgol@amuri.net]

Emacs freezes occasionally in such a way that sending it a DebugBreak
(see <https://cygwin.com/ml/cygwin/2006-06/msg00321.html>) has no
effect, and I have to kill it from the Task Manager (so I can not get a
backtrace).  When Emacs is in this state, it does not redraw its frames
when brought in focus.

In GNU Emacs 24.4.51.3 (x86_64-unknown-cygwin)
  of 2014-10-30 on [local build], Cygwin 1.7.33
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
  `configure --enable-checking --with-w32 --without-gnutls 'CFLAGS=-O0
  -ggdb''

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

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mail-utils jka-compr misearch
multi-isearch iso-transl network-stream starttls tls erc-track
erc-spelling flyspell ispell erc-services erc-ring erc-networks
erc-netsplit erc-menu erc-match erc-log erc-list erc-pcomplete 
pcomplete
erc-button erc-fill erc-stamp wid-edit erc-join erc-autoaway 
erc-goodies
erc erc-backend erc-compat format-spec auth-source eieio byte-opt
bytecomp byte-compile cconv eieio-core gnus-util mm-util mail-prsvr
password-cache thingatpt pp smex cl-extra vc-git paredit dired view
cc-langs cc-mode cc-fonts cc-guess cc-menus cc-cmds vc-dispatcher 
vc-svn
hideshow undo-tree diff python json info package epg-config server
cc-styles cc-align cc-engine cc-vars cc-defs appt diary-lib
diary-loaddefs cal-menu easymenu calendar cal-loaddefs advice help-fns
ido windmove header-file find-file gtags mu cl-macs edmacro kmacro cl 
gv
comint ansi-color ring saveplace paren savehist avoid time battery
desktop frameset cl-loaddefs cl-lib cus-start cus-load time-date 
tooltip
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
w32-common-fns disp-table w32-win w32-vars tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode prog-mode 
register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core frame cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer 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 make-network-process gfilenotify w32
multi-tty emacs)

Memory information:
((conses 16 433660 62998)
  (symbols 48 42289 0)
  (miscs 40 184 782)
  (strings 32 124600 12544)
  (string-bytes 1 2999027)
  (vectors 16 32403)
  (vector-slots 8 745322 66915)
  (floats 8 152 665)
  (intervals 56 15354 890)
  (buffers 960 61))