InstantiationContext.setExpandPack() and related methods were introduced
in bug 486971 to ensure that when instantiating a type list that
contains a pack expansion, with a parameter map that maps the template
parameter pack that appears in the expansion to another parameter pack
(which can happen when e.g. instantiating an alias template with
dependent arguments), the pack is expanded in the correct place.
However, bug 486971 only added use of this machinery to CPPTemplates.
instantiateArguments(). We can also instantiate a type list in
instantiateTypes() (used e.g. when instantiating the parameter types
of a function type), so the machinery needs to be used there as well.
Change-Id: Iabb458e8e3166c15ed922656fc0729a4a8cf8bbf
daad877559