Exclude non-hiragana chars from head of postfix katakana conversion target string.

* scm/tutcode.scm
  - (tutcode-postfix-katakana-acquire-yomi):
    Exclude non-hiragana chars from head.
Avoid an infinite recursion in GTK+ immodule.

* gtk2/immodule/gtk-im-uim.c
  - (update_cb): Apply the patch by tagoh.
    Don't emit a 'preedit_changed' signal
    when no preedit is started.
LINGUAS should list language name on each line

intltool's Makefile.in.in looks up specified language code using:

http://bazaar.launchpad.net/~intltool/intltool/trunk/view/head:/Makefile.in.in#L59
> USER_LINGUAS=(snip)if test -n "`grep \^$$lang$$ $(srcdir)/LINGUAS 2>/dev/null`"(snip)

This code snippet means that LINGUAS is expected to list each
supported language name on each line one by one.

This patch simply fix current LINGUAS to follow such manner and
let translation files properly generated.
Merge pull request #23 from naota/patch-1

LINGUAS should list language name on each line
Add XDG_RUNTIME_DIR support

Create a socket file under $XDG_RUNTIME_DIR/uim/socket if that env is available
Update comments
Merge pull request #24 from tagoh/master

Add XDG_RUNTIME_DIR support
Add "m17nlib-use-candidate-window?" option to the m17nlib module.

* scm/m17nlib-custom.scm
  - Use "m17nlib-use-candidate-window?" option.
* scm/m17nlib.scm
  - Define "m17nlib-use-candidate-window?" option
    based on the patch by icy in #25.