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.

void main()
{
    S t;
}

struct T
{
    int i;
    S* s;
}

struct S
{
    long i;
    T* t;
}