Add some alignment info where LLVM might otherwise be more pessimistic. In particular, %.nest_arg is always aligned even though it's bitcast from i8*. Pointers in vtables are also guaranteed to be stored at aligned addresses.

module bar;

class S
{
    int i;
    final int foo()
    {
        return i;
    }
}

void main()
{
    auto s = new S;
    s.i = 42;
    auto dg = &s.foo;
    assert(dg() == 42);
}