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 virtcall;

extern(C) int printf(char*, ...);

class C
{
    override char[] toString()
    {
        return "overridden";
    }
}

void main()
{
    C c = new C;
    auto s = c.toString();
    printf("%.*s\n", s.length, s.ptr);
}