gnome-control-center string changes

[Claude Paroz <claude 2xlibre net>]

Hi,

I just contributed a patch in gnome-control-center to use context for
event sound names.
http://bugzilla.gnome.org/show_bug.cgi?id=549489

I even dare to propose the new NC_ macro that will add some more msgctxt
in the pot file. For those using poedit, double-check your po file with
a text editor if you really want to distinguish the two "Logout" and
"Desktop" strings.

Claude