Remove some redundancy from the DValue hierarchy: all subclasses had a 'type' field and identical implementations of virtual function getType(). Move these to DValue itself, and make getType() non-virtual.

module condexp;

int f()
{
    return 42;
}

void main()
{
    int i = f() < 25 ? -1 : 1;
    /*int j = f() > 25 ? 1 : -1;
    assert(i);
    assert(!j);*/
}