Perfect forwarding

[Andrei Alexandrescu]

This topic came about during beerconf (it was fun!): Write an idiomatic 
template `forward` that takes an alias `fun` and defines (generates) one 
overload for each overload of `fun`. Example:

template forward(alias fun)
{
     ...
}

Now for this function:

void myfun(int, ref double, out string);
int myfun(in string, inout double);

the instantiation would be (stylized):

template forward!myfun
{
     void myfun(int a, ref double b, out string c)
     {
         return myfun(a, b, c);
     }
     int myfun(in string a, inout double b)
     {
         return myfun(a, b);
     }
}

So the challenge is implementing forward() to do this.