When checking a template argument list against a template containing

a parameter pack, check the parameter pack against each of the
template arguments it corresponds to, then pack the converted
arguments into a template argument pack. Allows us to use variadic
class templates so long as instantiation isn't required, e.g.,

  template<typename... Types> struct Tuple;
  Tuple<int, float> *t2;

llvm-svn: 122251