C++: Add a test with missing summaries.

Author: MathiasVP

cpp/ql/test/library-tests/dataflow/modelgenerator/dataflow/summaries.cpp

@@ -198,4 +198,14 @@ int get_x_from_union(U* u) {
 //contentbased-summary=;;true;set_x_in_union;(U *,int);;Argument[1];Argument[*0].Union[*U];value;dfc-generated
 void set_x_in_union(U* u, int x) {
     u->x = x;
+}
+
+struct HasInt {
+    int x;
+};
+
+
+int copy_struct(HasInt *out, const HasInt *in) {
+    *out = *in;
+    return 1;
 }