Fix VarDecls for tuples. Closes #99. I've implemented it this way since it doesn't require any changes in the frontend. However, I think having TypeTuple expressed as LLVM struct types would make much more sense and open the door to tuple lvalues.

module tuple1;

template Tuple(T...) {
    alias T Tuple;
}

struct S
{
    int i;
    long l;
}

void main()
{
    S s = S(Tuple!(1,2L));
    assert(s.i == 1);
    assert(s.l == 2);
}