[merge request] Many minor changes.

[Teika Kazura <teika lavabit com>]

Hi. Please merge my branch. It's not the "poweroff" fix of 1.7.0,
but applies to 1.7.1. It includes:

* Desktop environment detection cleanup.
* Translation
** po/README is written. Great!
** sawfish.pot had contained bogus entries. Removed them. (Will be explained.)
** po/update.sh accepts both ja and ja.po.
** Updated all po's.
* sawfish.el indents "let-fluids" and let-loop correctly.
** Using it, their indents are fixed. Now more readable.
* Matcher group minor change.

Regards,
Teika (Teika kazura)