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 bug7;

class love { }
void bug() {
    love[] child;
    child.length=1;
    assert(child[0] is null);
    child[0]=null;
    assert(child[0] is null);
}
void main()
{
    bug();
}