Support out/inout-parameters

[lhchavez]

For arrays only, since this will be hard to model outside of C for other types.

Example:

// example.idl:
interface Main {
};

interface example {
    void foo([Range(1, 1)] int N, [InOut] int[N] X);
};

// Main.cpp
#include "example.h"
#include <iostream>
int main() {
  int X[1] = {1};
  foo(1, X);
  std::cout << X[0] << std::endl;
}

In order to implement this functionality, the return messages need to be expanded to include the arrays after the return value. The implementation of [InOut] is different from [Out] just in that it performs the extra copy to supply the initial values of the array to the contestant's program.