Modify default C++ template to instantiate classes on heap

In C++ language, if we declare a large-sized array in the class to implement, the struct size of the class grows up. Hence we might get a stack overflow error if problem instances are instantiated on stack, rather on heap.

```c++
struct TheProblemDiv1 {
   int a[1000][1000];
};

void do_test() {
   TheProblemDiv1 instance; // Stack Overflow!
}
```

Topcoder's current behavior is, each class object is instantiated on heap, so we would expect the above code runs well (unless memory total used is exceeded).

Please modify the default C++ test code template, to instantiate the problem class on heap.