gvdb just dropped the ability to have a separate "options" field. We
now store the options into a GVariant along with the default value.
For now, we use a small shim in GSettingsSchema in order not to touch
too much code. A more complete rewrite will follow.
This represents a change to the schema file format with another likely
to follow. glib-compile-schemas needs to be re-run after installing
this change.
