String change in gtk-3-0 branch

[Federico Mena Quintero <federico ximian com>]

Dear translators,

I have just merged an interesting patchset to gtk+, in the gtk-3-0
branch.  This adds two or three new strings to the package; I hope that
doesn't cause too much trouble for you.

GTK+ hackers: this is the merge of the
bgo593793-filechooser-recent-folders branch, which is described in more
detail here:
http://people.gnome.org/~federico/news-2011-07.html#01

I'll backport this code to GTK+ 2.x so that apps which still use GTK+ 2
can get the goodness in the file chooser.

  Federico