Decrements the reference count for the type corresponding to the
interface default vtable
g_iface. If the type is dynamic, then
when no one is using the interface and all references have
been released, the finalize function for the interface’s default
class_finalize member of
GTypeInfo) will be called.
Available since: 2.4
The default vtable structure for an interface, as returned by
The data is owned by the caller of the function.