request to revert the chnage of revno 112925

[Kenichi Handa]

I'd like to revert the following change (revno 112925):

2013-06-11  Stefan Monnier  <address@hidden>

        * international/mule-conf.el (file-coding-system-alist): Use utf-8 as
        default for Elisp files.

By my recent changes for tuning up ASCII and UTF-8 file
reading, the speed for reading a UTF-8 file is almost the
same in the following cases:

* the file has coding: utf-8; tag
* find-operation-coding-system returns utf-8 for the file
  (the current case of *.el files)
* the file has no coding tag and utf-8 is the most preferred
  coding system
* the file has no coding tag and utf-8 is the most preferred
  coding system among 8-bit encoding (which means that such
  7-bit coding systems as iso-2022-jp may be more preferred)

So, the above change does not improve the performance that
much.

In addition, as iso-2022-jp and iso-2022-7bit have been the
most correctly detected coding systems in any environments,
there are many packages that uses them for *.el files (at
least in Japan).  Now many of them doesn't work.

In some sence, the above change is a regression because it
disables Emacs' facility to automatically decode ISO 2022
based 7-bit encodings, and we should notify users about such
a change in advance, for instance, by showing warnings by
byte-compiler for non-UTF-8 and no-coding-tag *.el files for
a while (perhaps while Emacs' version is 24.*).

---
Kenichi Handa
address@hidden