Fail to expand macro, comma in inner macro

Example code:
```
template <typename T, typename U>
U add(T num1, U num2) {
return (num1 + num2);
}
#define sum add<int, double>(2,2.5)
#define foo(a, b) a
#define result foo(sum,3)
result
```

simplecpp output:

11623.cpp:7: syntax error: failed to expand 'result', Wrong number of parameters for macro 'foo'.
