C++: Add new test case for template member change

We now output literals for accesses to members of template parameters:

So for `foo` in the following example:

```
template<typename T> void bar(T& t) {
  T.foo(1)
}
```

cpp/ql/test/library-tests/templates/CPP-172-template-members/test.cpp

@@ -0,0 +1,19 @@
+
+
+class A {
+public:
+  void foo();
+  int k;
+};
+
+class B {
+public:
+  template <typename T>
+  B(T x) {
+    int k = x.k;
+    x.foo();
+  }
+};
+
+A a;
+B b(a);

cpp/ql/test/library-tests/templates/CPP-172-template-members/test.expected

@@ -0,0 +1,2 @@
+| test.cpp:13:15:13:15 | k |
+| test.cpp:14:7:14:9 | foo |

cpp/ql/test/library-tests/templates/CPP-172-template-members/test.ql

@@ -0,0 +1,4 @@
+import cpp
+
+from Literal l
+select l