Fix marking of translatable strings for gettext

was broken in:

commit 6d2ab577c41c9b07a84c049137c8184bb67f5e30
Author: Caius 'kaio' Chance <me@kaio.net>
Date:   Fri Oct 5 10:40:47 2012 +1000

    Refactor _refresh_properties() function.
update zh_??.po files
Add German translation
Add some generated files to .gitignore
Do not fail if the ~/.ibus/byo-tables/ directory does not exist

“/usr/libexec/ibus-engine-table --xml” aborted with an error
if ~/.ibus/byo-tables did not exist.
Merge remote-tracking branch 'mike-fabian/some-fixes-for-rel20121101' into 1.5.0