The injected-class-name of class templates and class template

The injected-class-name of class templates and class template
specializations can be treated as a template. Finally, we can parse
and process the first implementation of Fibonacci I wrote!

Note that this code does not handle all of the cases where
injected-class-names can be treated as templates. In particular,
there's an ambiguity case that we should be able to handle (but
can't), e.g.,

  template <class T> struct Base { };
  template <class T> struct Derived : Base<int>, Base<char> {
    typename Derived::Base b;       // error: ambiguous
    typename Derived::Base<double> d;  // OK
  };

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@67720 91177308-0d34-0410-b5e6-96231b3b80d8