Eliminate a silly little Parse/Sema dance when parsing typename

specifiers such as

  typename T::template apply<U>

Previously, we would turn T::template apply<U> into a
TemplateSpecializationType. Then, we'd reprocess that
TemplateSpecializationType and turn it into either a
TemplateSpecializationType wrapped in an ElaboratedType (when we could
resolve "apply" to a template declaration) or a
DependentTemplateSpecializationType. We now produce the same ASTs but
without generating the intermediate TemplateSpecializationType.

The end goal here is to avoid generating TemplateSpecializationTypes
with dependent template-names, ever. We're not there yet.

llvm-svn: 126589