Documentation

Remove functions and methods annotated with "moved-to".

GObject-introspection does not currently support nullability annotations, so we try to guess the nullability from the nullability annotations of the curresponding get/set methods, which in principle should be reliable.

Not every interface that provides signals/properties is marked as requiring GObject, but this is necessarily the case, so fix the introspection data accordingly.

Some libraries include duplicated flags by mistake, drop those.

Sometimes arguments are marked as being a user_data destructor, but there is no associated user_data argument. In this case we drop the annotation.

Some symbols have names that are not valid Haskell identifiers, fix that here.