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 mini.delegate2;

void main()
{
    int foo = 42;
    int bar()
    {
        return foo;
    }
    int delegate() dg = &bar;
    assert(dg() == foo);
}