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 tangotests.switch2;

void main()
{
    int i=0;
    switch(i)
    {
    case 0:
        return;
    case 1:
        return;
    default:
        assert(0);
    }
}