This changes init_dom_node_() to take an allocated argument saying whether
to allocate or not. If the value is -1, node->allocated will be set to the
value of node->parent->allocated. This way the value is inherited like we
do it in the menu code. It should be a sane default since we eventually
want not to rely on the 'underlying' source of the document and there will
be less variables to pass around.
