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 structinit2;

struct Imp
{
    int i;
    long l;
    float f;
}

void main()
{
    Imp i;
    assert(i.i == 0);
    assert(i.l == 0L);
    assert(i.f !<>= 0.0f);
}