Introduce a new expression kind, SubstNonTypeTemplateParmPackExpr,
that captures the substitution of a non-type template argument pack
for a non-type template parameter pack within a pack expansion that
cannot be fully expanded. This follows the approach taken by
SubstTemplateTypeParmPackType.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123506 91177308-0d34-0410-b5e6-96231b3b80d8