Intl.DisplayNames v2 adds "calendar" and "dateTimeField" types, as well
as a "languageDisplay" option for the "language" type. This just adds
these options to the constructor.
Intl.DisplayNames was the first Intl object implemented, and at that
point all AOs were just put into the main Intl AO header. But AOs that
belong to specific objects belong in that object's header. So this moves
CanonicalCodeForDisplayNames to the Intl.DisplayNames header.
