bug#16125: 24.3.50; build failure

[Katsumi Yamaoka]

The recent change in regex.c (r115491) causes an error when
bootstrapping bootstrap-emacs on Cygwin (at least?).
Reverting it works around.

if test "no" = "yes"; then \
  rm -f bootstrap-emacs.exe; \
  ln temacs.exe bootstrap-emacs.exe; \
else \
  ./temacs --batch --load loadup bootstrap || exit 1; \
  test "X" = X ||  -zex emacs.exe; \
  mv -f emacs.exe bootstrap-emacs.exe; \
fi
Loading loadup.el (source)...
Using load-path (/Work/emacs/lisp /Work/emacs/lisp/emacs-lisp 
/Work/emacs/lisp/language /Work/emacs/lisp/international 
/Work/emacs/lisp/textmodes /Work/emacs/lisp/vc)
Loading emacs-lisp/byte-run...
Loading emacs-lisp/backquote...
Loading subr...
Loading version...
[...]
Loading /Work/emacs/lisp/startup.el (source)...
Loading /Work/emacs/lisp/ldefs-boot.el (source)...
Invalid regexp: "Invalid content of \\{\\}"
Makefile:811: recipe for target 'bootstrap-emacs.exe' failed


In GNU Emacs 24.3.50.1 (i686-pc-cygwin, GTK+ Version 3.8.2)
 of 2013-12-13 on localhost
Bzr revision: 115496 rgm@gnu.org-20131212224131-2bqe6eaps7ml2pq1
Windowing system distributor `The Cygwin/X Project', version 11.0.11404000
Configured using:
 `configure --verbose --with-x-toolkit=gtk3'