Tuples in LDC - why it does this?

[rikki cattermole]

Works in both with -betterC as per spec:

```d
import std.typecons;
import std.meta;

Tuple!(int, int, int) iAMfunction() {
     return tuple(1, 2, 3);
}

extern(C) int main() {
     int a, b, c;
     AliasSeq!(a, b, c) = iAMfunction();
     return 0;
}
```