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 bug19;

void main()
{
    auto dg = (int i) { return i*2; };
    assert(dg(2) == 4);
}