C++: Fix specialization resolution for nested types

Use-cases:

template<typename T>
struct Traits { typedef typename T::pointer pointer; };

template<typename _Tp>
struct Traits<_Tp*> { typedef _Tp *pointer; };

struct Foo { int bar; };

// 1
template<typename T>
class Temp
{
protected:
   typedef Traits<T> TraitsT;

public:
   typedef typename TraitsT::pointer pointer;
   pointer p;
};

void func()
{
   Temp<Foo *> t;
   t.p-> // complete
}

// 2
class Temp2
{
protected:
   typedef Foo *FooPtr;
   typedef Traits<FooPtr> TraitsT;

public:
   typedef typename TraitsT::pointer pointer;
   pointer p;
};

void func2()
{
   Temp2 t;
   t.p-> // complete
}

Task-number: QTCREATORBUG-14141
Change-Id: Id3459671117c0c81bcde7c9714b42750634c0225
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>