Reinstate the introduction of source-location information for

nested-name-speciciers within elaborated type names, e.g.,
 
  enum clang::NestedNameSpecifier::SpecifierKind

Fixes in this iteration include:

  (1) Compute the type-source range properly for a dependent template
  specialization type that starts with "template template-id ::", as
  in a member access expression

    dep->template f<T>::f()

  This is a latent bug I triggered with this change (because now we're
  checking the computed source ranges for dependent template
  specialization types). But the real problem was...

  (2) Make sure to set the qualifier range on a dependent template
  specialization type appropriately. This will go away once we push
  nested-name-specifier locations into dependent template
  specialization types, but it was the source of the
  valgrind errors on the buildbots.
  

llvm-svn: 126765