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 bug38;

void func(int* p)
{
    p++;
}

void main()
{
    int i;
    func(&i);
}