bug#18141: 24.4.50; saving .gz file breaks file coding

[Katsumi Yamaoka]

Hi,

Say there is a file containing non-ascii characters like this:

;;; test.el -*- coding: iso-2022-7bit; -*-
(message "テスト")

When I save this to test.el.gz, `buffer-file-coding-system' is
changed to `no-conversion' and I can see the contents are not
encoded (IOW, encoded by `utf-8-emacs') in that file.  This
happens not only with an ELisp file (try the etc/HELLO file).
No problem on Emacs 24.3.

Thanks.

In GNU Emacs 24.4.50.1 (i686-pc-cygwin, GTK+ Version 3.10.7)
 of 2014-07-28 on localhost
Repository revision: 117589 eliz@gnu.org-20140727180537-6lspaeedou1tg2xr
Windowing system distributor `The Cygwin/X Project', version 11.0.11501000
Configured using:
 `configure --verbose --with-x-toolkit=gtk3'