[svn r328] Fixed an issue with interfaces where the vtable type of a interface implemented could be invalid. Fixes several tango modules like, FileStream, ServerSocket and most tina cluster modules :)

module tangotests.nested1;

void main()
{
    int i = 42;
    assert(i == 42);
    void func()
    {
        assert(i == 42);
    }
    func();
}