This is meant as an input to the font chooser.
We don't want the user to select a language, but
rather have fonts presented as they would work for
the current language. Therefore, do away with the
lang/script combo on the tweak page.
We must notify the font and font-desc properties when the
list selection changes, and return NULL values for them
when there is no selection in the list.
Previously, we would pango_font_describe() every time the code ran and
we wouldn't ever hit the optimized quick exit.
The code now is a lot more complex because the
compute-actual-value-when-required-the-first-time approach is not
supported out of the box in GtkTreeModel (or GValue).
This subdirectory gets in the way when integrating the inspector
build more fully with GTK+, and does not really add anything.
Just move everything one level up.
