This significantly simplifies everything -- because a single type can
now handle both StringView lists and char* lists, we no longer need a
templated private helper to avoid allocating a temporary array of
unified type. Instead, the whole extension initialization can be done
directly in the initialize() helper, by simply iterating over the
argument.
Yay, this is probably the nicest improvement caused by StringIterable so
far.
Vladimír Vondruš